The rubber stamp has a mind of its own. WESTMINSTER JOURNAL

WALTER BAGEHOT, the 19th-century scholar of Britain's unwritten constitution, once declared that ``the best cure for admiring'' the House of Lords ``is to go and see it.'' Over the years, the upper house of the ``mother of parliaments'' has been considered a citadel of aristocratic reaction, a ``Sunset Boulevard'' for politicians of pensionable age, and a constitutional rubber stamp. But despite such barbs and brickbats, the House of Lords has survived. In recent years it has even appeared to flourish. Now, suddenly, it is a focus of argument.

The stimulus for this surge of controversy about a chamber that traces its origins back to the Middle Ages was a decision by Prime Minister Margaret Thatcher last month to summon an army of hereditary peers from the countryside to dig her out of a political fix. She asked them to vote down a threatened rebellion in Lords over her plan to reform the system of local taxes and replace them with a per capita, or poll, tax.

When these Tory ``back-woodsmen'' - most of whom never darken the portals of the upper chamber from one year's end until the next - arrived to do their Tory duty by voting down an amendment of the poll tax bill, Britons were reminded that the House of Lords remains an undemocratic body with a built-in right-wing majority.

Tony Benn, a radical Labour MP who renounced his family title as Lord Stansgate in the early 1960s in order to remain an active politician, used the incident to expound his view that the Lords should be abolished.

Mrs. Thatcher, Mr. Benn believes, has hastened the day when the Lords must bow to the modern era and either accept drastic reform or quit the parliamentary stage altogether.

The ``other place,'' as the upper chamber is known to members of the House of Commons, used to be the dominant wing of Parliament. But its powers were greatly weakened by reform acts in the 19th century, and all but wiped out in 1911 when the elected lower house won control of financial legislation.

At that point, the Lords had to settle for a restricted role as a reviewing and delaying chamber. They have retained their luxurious trappings (robes of ermine on great occasions) and arcane parliamentary procedures (peers do not vote ``yes'' and ``no,'' but ``content'' and ``not content''). But the house is only allowed to debate bills, not to prevent them from becoming law. In this circumscribed function, it tended to draw more amusement than respect. The upper house seemed more like a privileged club than a serious organ of government.

Aged hereditary peers would stage often perfunctory debates in their ornate chamber. As they talked, the bewigged Lord Chancellor, their chairman, at times slumbered on ``the Woolsack,'' a seat resembling a big red ottoman with a back rest. It was common for the Lords to begin their daily sitting at 2:30 after a good lunch and rise less than an hour later in anticipation of an agreeable afternoon tea. No wonder Benjamin Disraeli, when he retired to the upper chamber, said ``I am dead - but in the Elysian Fields.''

But despite the apparent irrelevance of the Lords, there was always a feeling that Britain needed an upper house.

Twelve years after World War II, the Lords gained a new momentum when it was decided to create ``life peers.'' Chosen by the prime minister, such peers - who include women - are not able to pass their titles to their offspring. But in most other respects, they enjoy the status and privileges of lords of the realm.

The immediate effect of this move was to inject much-needed new blood into the second chamber in the shape of recently retired Cabinet ministers and Commons backbenchers, as well as senior retired businessmen. Debates sharpened as a group of ``working peers,'' many of them experts in their respective fields, warmed to the task of reviewing bills. This group (some 300 in number) undertook most of the debating and committee work.

Then the House of Lords got another boost - from the electronic media. In 1985 cameras were allowed into the upper house as an experiment. They have been there ever since.

As a result, many British viewers were persuaded that the upper chamber was not as moribund as they had thought. The effect on the peers themselves was electrifying. Aware that the eyes of the people were on them, some of them began flexing their political and constitutional muscles by challenging bills on education, health, and local government. Occasionally they forced the government, which enjoys a majority of over 100 in Commons, to rethink its legislation.

Because the House of Lords has become more important and somewhat unruly, Mrs. Thatcher has had to ensure that her supporters there are well led. When her deputy, William Whitelaw, retired from the Commons, the prime minister made him Viscount Whitelaw and leader of the Tory majority in Lords. A few months ago, however, poor health forced Whitelaw to give up that post.

When Thatcher's poll tax bill came before Parliament, some of her own supporters in the Lords - aware that Whitelaw was not there to keep them in line - muttered about the unfairness of the new tax. They threatened to stage a serious protest against it.

So great was the brewing brouhaha that the prime minister ordered Lord ``Bertie'' Denham, the government's chief whip in the upper house, to send messages out into the countryside, requesting the presence of Tory peers who do not normally turn up at Westminster.

Among those heeding the call were such little-seen figures as the 13th Earl of Rollo - ex-Eton, ex-Grenadier Guards, aged 72 and normally content to tend his 700-acre estate in Perthshire, Scotland. As he climbed off the night sleeper Lord Rollo was reported as saying: ``I come to London very rarely: I can't stand the smell of petrol and oil.''

The result of this aristocratic influx was a crushing victory (317 votes to 183) for the government. But the scale of the victory has stirred a debate about the future of the Lords.

It's now clear that the advent of the ``life peer'' had hidden an obvious fact about the House of Lords: While there appeared to be a reasonable balance between the political parties in the House of Lords among the ``working peers,'' this was achieved by arranging for most hereditary peers, as one commentator put it, to ``lie sleeping in the shires.''

Lord Gifford, an opposition peer, said the vote on the poll tax ``ought to destroy the illusion many have had that the Lords can serve as a check on a doctrinaire government of the right. If the Conservatives choose to muster their natural majority of hereditary Lords, they can always win.'' Gifford wants to see the Lords replaced by a senate made up of elected members representing large regional constituencies.

But things are not apt to change much. Part of the reason is that there is little enthusiasm for reform within the opposition Labour Party.

Present Labour leader Neil Kinnock has ruled out reform of the Lords as a policy item for his party at the next general election. He believes the electorate would consider such a proposal to be too radical. Former Labour Prime Minister James Callaghan strongly opposed reform of the Lords while in office; nowadays, as Lord Callaghan, he is an active and vocal member of the upper house. His Labour predecessor, Lord Wilson, is likewise unenthusiastic about reform.

Some Tories believe that Labour does not want a reformed (and more effective) House of Lords, because this would diminish the status and authority of the Commons. This theory holds that Labour, if returned to office, would prefer a compliant upper chamber.