William Hague, the embattled Tory leader faced further humiliation yesterday as former Chancellor Kenneth Clarke launched another scathing attack on the right-wing direction of the Tory party only hours after a Tory candidate for London mayor distanced himself from Mr Hague's leadership.

As Labour party sources contemplate a third term of office in the face of such a fractured Tory party, the pro-European Mr Clarke warned Mr Hague that the Tories had not yet begun to rebuild themselves as a ''credible party of Government''.

Mr Clarke, who fears the Tories have been hijacked by ''right-wing idealogues'' making them as unelectable as the Labour Party of the early eighties, has already accused Mr Hague of departing from Tory principles.

But in BBC Radio 4's World at One programme he went further, condemning the party's lurch to the right. While his contempt for the young right-wingers in the party is well known the timing of his comments, amplifying complaints from former Tory front bencher Shaun Woodward who two weeks ago defected from the Tories to the Labour benches, could hardly be worse.

Labour seized on Mr Clarke's comments. ''This devastating - and accurate - analysis of William Hague's weaknesses as a leader comes from one of the few big hitters left in the Tory Party,'' said Cabinet Office Minister Ian McCartney.

''Coming so soon after Shaun Woodward's defection to Labour, Ken Clarke's criticism of the Tories' rightward lurch under William Hague confirms that the Tories are now more extreme than they have ever been.''

Mr Clarke privately hopes he will be able to change the direction of the party ''when it comes to its senses'' but fears that Conservative Associations throughout the country are selecting only right-wing candidates.

Mr Clarke's own Rushcliffe Association has tried to rein in his criticism, but yesterday he abandoned caution, calling on Mr Hague to try to reconnect with the party's heartland, which had transferred its support to Labour. Urging Mr Hague to ditch his hostility to Europe, while finding policies which empathise with the aspirations of the British public, Mr Clarke condemned the ''mad obsession'' with Europe.

''Get rid of some of the ideology and stop this mad obsession with Europe when everybody knows that the future of this country is destined to be playing a constructive role in the European Union,'' he said.

Meanwhile, Mr Andrew Boff, the contender Mr Steve Norris has to beat to win the Tory nomination for the London mayoral race, blew what little chance he every had of winning by distancing himself from the Tory leadership.

Calling a press conference to set out his ''independent credentials'', he refused to be bound by future Tory manifestos.

He said: ''My candidacy is the only true independent choice voters will have in London. I will not be bound by collective responsibility of the Shadow Cabinet. I will not be bound by the Conservative manifesto at a future General Election.

''This is the Boff campaign which is seeking support of London Conservatives. I believe it is important that this independent stance is emphasised.''

Last night the Tory hierarchy dismissed Mr Boff's protestations since they believed he had little chance of making any impact in the nomination race but they were furious at Kenneth Clarke who still has a supportive constituency within the Tory party.

A senior Tory source reminded Mr Clarke that he had been a member of the Government responsible for the worst parliamentary defeat for 160 years.