Alistair Darling has admitted that under Iain Gray’s leadership of the Scottish Labour Party the SNP Government has been allowed a free run at Holyrood.

In an exclusive interview with The Herald, on the eve of the Labour conference in Brighton, the normally reserved Chancellor also unleashes a passionate rallying cry to parliamentary colleagues, urging them not to “curl up in ball, say everything is terrible and blame someone else”.

In an implicit criticism of Mr Gray – his former spin doctor at Westminster – the Chancellor acknowledges First Minister Alex Salmond has been given an easy ride in the Scottish Parliament.

Mr Darling says: “The Nationalists have had two years where they have not been exposed to particular criticism or questioning in many cases but people can see for themselves that it’s very tempting to blame someone else. People in Scotland are not daft. They voted by one seat to change the administration two years ago but the idea that a separate Scotland breaking away from its largest neighbour makes any sense in today’s world is just nonsense.”

The thinly-veiled reproof to the Labour leader in Edinburgh will do nothing to bolster Mr Gray’s position, which has been the subject of private misgivings among colleagues, who regard him as having made little political headway against the First Minister in the 12 months he has led the party at Holyrood.

The Chancellor admits the UK Government can do better yet insists it is still able to win the General Election, despite trailing by 14 points in the polls.

“I have no intention after 12 years in government and 18 in opposition to stand back and hand it all over to people, who in their hearts have exactly the same approach that got the country into a mess in the past. We have to come out and fight for what we want. The people want to see some sparks, some fight and enthusiasm and, if we can demonstrate that, we’ve got every chance of winning the big argument,” declares Mr Darling.

He warns a Tory government would use the financial crisis simply as an excuse for blanket spending cuts. “If it hadn’t been this crisis, they would have found some other reason to do it. The Tories were profoundly wrong to oppose everything we have done to support the economy, wrong to equivocate on the question of stabilising the banking system and they are wrong now to argue that we should withdraw support for the economy, and particularly helping people get back into work just when we’re coming through to recovery,” adds the Chancellor.

Next week, Gordon Brown will seek to use his last party conference before the election to bolster his leadership, inspire Labour troops and silence his critics. In his keynote speech, he will underline his “frontline first” policy by revealing that Health Secretary Andy Burnham has found £1bn of savings to improve cancer care and help save 10,000 lives a year.

“With our early treatment guarantee of a specialist within two weeks and our early diagnosis guarantee of tests within one week, the NHS will offer some of the best cancer care anywhere in the world.

“Our ambition could not be greater: step by step to beat cancer in this generation,” the PM is due to say.

While Downing Street spoke of the guarantee applying “across Britain”, given health is devolved, it will not apply to Scotland.