Justice minister Jonathan Djanogly hired detectives to spy on aides

The political future of the Justice minister Jonathan Djanogly was in the balance last night after he provoked fury by hiring private detectives to spy on Tory activists in his constituency.

Downing Street gave its qualified support to Mr Djanogly, who apologised for ordering the covert operation to see if aides and colleagues were responsible for planting damaging stories about him in the press. But one of the senior Tories targeted by the investigators urged Mr Djanogly, the MP for Huntingdon, to "consider his position" in Government.

Derek Holley, the former leader of Huntingdon Council, said: "Quite frankly, I was just appalled by it all. I have been in local politics and associated with national politics for 34 years, and I have never, ever experienced anything like this in the whole of that time."

The Prime Minister's official spokesman said David Cameron regarded the matter as closed and retained full confidence in his minister. But, in a less than ringing endorsement of Mr Djanogly's long-term career prospects, he added: "The PM will judge him on his performance as a minister." Government sources later said there was no immediate prospect of the minister being sacked, but acknowledged Mr Djanogly faced unrest in his constituency. One source said: "The biggest threat to him is locally."

The MP hired the private detectives last year, when he was shadow Solicitor General, to gauge the opinions of prominent Tories in Huntingdon about his performance. He is said to have paid the company Morris Chase International more than £5,000 to trick them into talking about him under the pretence of writing a newspaper article. The firm stressed its activities were entirely legal and in accordance with the Data Protection Act.

Its report is understood to have concluded that aides thought he was a poor politician and had lied over his expenses. It was reported to show that his election agent, Sir Peter Brown, resigned over the "expenses scandal" and not, as suggested at the time, because of ill health.

In a statement, Mr Djanogly said: "Following a series of malicious allegations made against me in newspapers last year, I felt I had to act to find out who was spreading these untrue stories. I instructed a firm of private investigators to try to find out the source of these stories because I was extremely upset that my private family life had been invaded."

He said he would never have "contemplated condoning anything unlawful or dishonest" in the investigation, but added: "I am sorry if some people judge that I made a mistake. With hindsight I can see that I may have over-reacted, but I was being subjected to very malicious, anonymous attacks on my family."

Mr Cameron will be anxious not to lose his second minister following the resignation of David Laws as Treasury Chief Secretary three months ago. But the affair will raise question marks over Mr Djanogly's prospects of surviving in the next ministerial reshuffle.