Theresa May has been ordered to raise her game by a Conservative MP and former minister who says her government is guilty of “timidity and lack of ambition”.

Nick Boles launched an extraordinary attack on his party leader on Twitter, listing the controversy over the release of John Worboys, the housing crisis and NHS funding as key areas of concern.

The politician has been delivering a critique of government policy in recent months through the publication of a series of chapters from his new book, Square Deal, about how to revitalise modern Conservatism.

But he appeared to snap over the decision of the justice secretary, David Gauke, not to seek a judicial review into the Parole Board’s decision to free Worboys after less than 10 years in prison. The 60-year-old taxi driver was jailed in 2009 for assaults on 12 women in London. The government had looked into the possibility of a legal challenge but decided against it after consulting lawyers.

Boles told the Guardian: “We need ministers to have the courage of their convictions and not be bamboozled by the advice of officials trying to justify the system.”

It came after he tweeted:

Nick Boles MP (@NickBoles) There is a timidity and lack of ambition about Mrs May's Government which means it constantly disappoints. Time to raise your game, Prime Minister. #worboys #HousingCrisis #NHSfunding #etcetc

The MP, who returned to constituency work in September after battling cancer, argued that the Worboys decision was the final straw because a judicial review would have been an opportunity for ministers to express their anger. He said they should have pushed ahead even if there was only a 10% chance of victory.

His book has called for a bolder approach to economic, housing and health policy, demanding the Tories bring an end to the “age of austerity” and focus on investment and driving up productivity. The former skills minister said that would help tackle the lack of growth in wages.

He has also suggested re-branding national insurance to fund the NHS and social care.

Boles, who was a key figure in Michael Gove’s unsuccessful leadership bid, told the Sun that he wanted Downing Street to “pull their finger out” and for May to lead, be bold and definite. “When I came back, I said we needed a new story, a new set of ambitions. I put it in friendly terms and I just feel we’re moving backwards,” he said.