New Justice Secretary David Lammy should take immediate action to stop a “crime wave” being unleashed on the nation’s streets, his Conservative opposite number Robert Jenrick has warned.

Mr Jenrick fears up to 43,000 criminals will escape a prison sentence as a result of Labour’s plans set in motion by his predecessor, the new Home Secretary Shabana Mahmood.

He said: “Lammy has an opportunity to stop a crime wave from being unleashed on our streets. Or he can go along with it and be remembered as the man who surrendered the Chagos islands and surrendered our streets to criminals.”

Labour’s changes will introduce a presumption against jailing people for less than a year. Its radical prison shake-up means some criminals will be released a third of their way through sentences if they behave well and take part in rehabilitation schemes – and some serious criminals will only have to serve half their sentences rather than two-thirds.

Mr Jenrick said: “The first thing David Lammy should do when he gets to his desk is rethink Labour’s dangerous Sentencing Bill. It will see up to 43,000 criminals avoid prison every year – that’s over half of all criminals sent to prison each year.”

The former Tory leadership candidate – who is concerned the country could sink into a full-scale financial crisis – gave a withering verdict on Sir Keir Starmer’s reshuffle in the wake of Angela Rayner’s resignation as Deputy Prime Minister.

He said: “This Government is little over a year old and already it’s in chaos. Starmer’s decision to move Yvette Cooper from the Home Office is an admission that Labour have failed abysmally to stop the boats and the problem is getting worse. But shuffling the deck of ministers won’t change anything because Starmer is the problem and is blocking necessary change.

“He still clings to outdated international treaties that have become charters for criminals at the expense of the British people. He can try and blame others but the buck stops with him.”

Warning that the situation is likely to get worse, he said: “The chaos the Government is in today is a small taste of what is to come unless Starmer changes course. Sir Keir’s attempts to curb the benefits bill have failed spectacularly and it now threatens to bankrupt the country.

“Unless he changes course we are on course for a 2008-style crisis that will leave everyone poorer.”

A Labour source said Mr Jenrick had “some brass neck”, saying: “However hard he tries, the public can see right through his flagrant attempts to distance himself from his own record. The last Conservative government managed to add fewer than 500 prison places to the entire estate in 14 years, taking the criminal justice system to crisis point.

“They have zero credibility on law and order. As Deputy Prime Minister and Justice Secretary, David Lammy will ensure that victims are protected and there is always space to lock up criminals.”