Former Tory Cabinet minister Ken Clarke has questioned the strength of the recovery, claiming it is "not firmly enough rooted" in a balance between manufacturing and services.
The former Chancellor, who retired from the Government in the reshuffle, warned the economy remained "fragile" and vulnerable to shocks.
In an interview with The Observer, the Europhile veteran MP admitted to tensions with David Cameron since 2010 and claimed the Tory press office had tried to keep him away from the TV cameras.
Mr Clarke, 74, who served as justice secretary and minister without portfolio until last week's reshuffle, said of the recovery: "It's not firmly enough rooted on a proper balance between manufacturing and a wide range of services and financial services.
"I mean, we have this mystery of why we can't get productivity to start rising again."
Mr Clarke said he was a "great fan" of George Osborne and insisted the coalition had saved the country from economic disaster by reining in spending.
He said: "We're only halfway through ... We've saved the country from calamity but we've got a long way to go before we get a competitive economy, with sustainable levels of growth and all that."
Mr Clarke warned about the "ludicrous cycle" of housing booms and crashes, but said Bank of England governor Mark Carney was addressing the problem.
He said his own appointment after the 2010 election as justice secretary "turned out to be a slight mistake" because "unfortunately my views didn't coincide with No 10's ... David and I didn't fall out exactly, (but) there was constant friction".
Mr Clarke, who has vowed to play a leading role in fighting to keep the UK within the European Union in the referendum promised by the Prime Minister by the end of 2017, said the Conservatives had become divided on the issue again.
"I belong to a Conservative party that used to be able to win elections ... it was the self-discipline of the party that was extraordinary," he said.
But a lot of Tory MPs now saw being a member of the governing party as "a secondary consideration" to attacking the EU, he claimed.
Winning a majority in next year's election was a "mountain to climb", he acknowledged.
Mr Clarke complained that Tory spin doctors had tried to keep him away from the media - including once telling the BBC he was too ill to go on Question Time.
When he rang the producer "she said, 'I'm told you're ill'. After that I got even more freelance."
Shadow treasury chief secretary Chris Leslie said: "The former Conservative chancellor is admitting the truth about the economy which David Cameron and George Osborne refuse to acknowledge.
"After saying last month that most people aren't feeling any sense of recovery, Ken Clarke now also admits the recovery is unbalanced and not rooted.
"If we're to get a strong and balanced recovery which everyone benefits from, we need Labour's plan to tackle the cost-of-living crisis and reform our economy for the long term. The same old Tory answers will never be able to address the low skills and low productivity economy Ken Clarke is rightly warning about."