LONDON -- Problems over Europe threatened to topple another British prime minister on Thursday as a withering attack on John Major's leadership undermined his already weak position.


The latest crisis was sparked by Major's handling of a row with the European Union over voting rights which led a maverick parliamentary colleague on Tuesday to call for his resignation. Other critics quickly joined a chorus of demands for the prime minister's head.


Only a week ago Major was talking tough, insisting he would not back down on raising the Union blocking minority to 27 votes from 23 -- diluting Britain's ability to stand in the way of legislation it opposes. On Tuesday he agreed to the change.


Critics argue he not only gave in on an issue of sovereignty but handled it ineptly.


Conservative Party figures tried to shore up Major with interviews throughout the day, but once loyal newspapers that have steadily turned against him saw it differently. "Major Facing Leader Crisis" screamed the Daily Express, the last mainstream paper to back Major.


Jitters over the political uncertainty ran through financial markets. Sterling fell a pfennig to a five-month low at 2.48 German marks, depressed by the crisis, dealers said.


Tony Marlow, a Conservative anti-European M.P. little known outside parliament, plunged a verbal knife deep into Major on Tuesday, saying his EU retreat left him discredited


"Why doesn't he stand aside and make way for somebody else who can provide the party and country with direction and leadership?" asked Marlow.


Marlow may be a relative nobody but his outspoken attack in parliament -- the first on a sitting prime minister by one of his own members for at least 30 years -- summed up a deep-seated concern about Major on the backbenches of the Conservative Party.


Three and a half years after replacing Thatcher, Major has failed to put his mark on the premiership in a way that can unite a party bitterly divided over closer ties with Europe and over the way Thatcher was unceremoniously dumped.