Robin Cook has denied he harbours ambitions to lead the Labour Party.

The former Commons leader, who resigned from the Cabinet in March over the war against Iraq, said in an interview on Sunday that he will never stand for Tony Blair's job.

But in a renewed attack on his former colleagues, Cook claimed Labour is abandoning the working class.

Cook has been tipped as the leader of a left-wing revolt against Blair following his forensic criticisms of the government's Iraq policy.

But he has denied plotting against the party leadership and ruled out ever standing for the top job.

"There is no vacancy, and believe me when the vacancy comes round it will be a crowded field of very good candidates and I have no intention of being among them," he told GMTV's Sunday Programme.

"I've had a very good career in politics, and I intend to continue being a very useful member of the parliament and helping my party in the debates and some of the issues as to where it should go but I'm a man who has achieved...what I set out to do and I've been up there at the top of the party and I'm very happy with that."

The former foreign secretary hinted that he may yet return to frontline politics but says he is happy with what he has achieved already.

"I've gone further than I would have hoped about as a teenager and that's good, that's fine," he said.

"If I can serve my party in the future, of course I'll consider that, but...not plotting, I'm not planning."

In a move that will cause concern in Downing Street, Cook also warned that Labour is not paying enough attention to its traditional supporters.

Already rocked by his calls for a public inquiry into claims that the government "sexed up" intelligence information on Iraq, ministers may fear that a groundswell of support is building up for the Livingston MP as a rallying point for disaffected party members.

In the interview Cook widened his critique of the government to say that it does not promote its policies for the poor loudly enough for fear of alienating the middle classes.

He warned that the coalition between "aspirational" middle class voters and the solid traditional Labour vote was in danger of breaking up.

"I think the great success of Tony Blair was he created a coalition between the middle class, aspirational classes, and the solid traditional Labour party vote, among the working class and among some of the deprived estates," he said.

"What he risks now is the coalition coming apart, not because of desertion by the middle classes and the aspirational classes, but because the stronghold, traditional Labour vote, those in the deprived vulnerable estates, feel that they have not had enough attention paid to them, feel that the government's not speaking for them, is not representing them."

Cook praised many of Labour social policies but fears that party supporters are losing faith in Labour because they have not been told about them.

"We've actually done an enormous amount for those people, a tremendous amount," he said.

"Redistribution through the tax credit, increase in housing benefit, increase in pensions for those that are poorer, the work we've done in neighbourhood renewal - but we tend not to put that in lights as our headline issue.

"They tend not to be the people with whom Tony Blair and others are seen photographed, visiting, expressing concern."

Cook said that the rest of the parliament should be devoted to winning back Labour's traditional support, many of whom feel alienated and angered by policies on Iraq, tuition fees and foundation hospitals.

"I think for the remainder of this parliament, the government needs to invest more effort in that wing of the coalition because yes, Tony Blair's analysis is absolutely right, we only win when we've got both parts of that coalition working for us, but we need to make sure that we keep the stronghold vote as well as the aspirational vote," he said.

And at the end of week in which he is reported to be writing a book on Britain's road to war with Iraq, Cook called again for an outside inquiry into the legal basis for the conflict.

Expressing his concern for the independence of parliamentary intelligence and security committee investigation that has been given the green light by the government, the man Blair first put in charge of MI6 said a judicial review would have been more suitable.

"I would have preferred something more open, more transparent," he said.

"Indeed, I would've preferred somebody from outside the political circle, somebody like a judge for instance who is accustomed and skilled in sifting evidence.

"I think the government's credibility may start to get stretched, if they continue to deny [this] reality."