Former Home Secretary Jack Straw said delays in the 'plebgate' investigation risked bringing the police into disrepute.
He told BBC Radio 4's Today programme: "We're not police officers, we're not investigators.
"What I've said in my letter to Theresa May is that whilst as the Home Secretary, as I know very well, it's not appropriate to seek to influence the outcome of an investigation, it is certainly appropriate, certainly in my experience a lot, to find out what is going on in an investigation.
"In particular why delays are taking place, which frankly have the risk of bringing the police into some level of disrepute and that is a responsibility of the Home Secretary."
More top news
A hitchhiking robot that won the hearts of fans worldwide has met an untimely end after being vandalised on its trip across the US.
Rules could be changed to remove support for failed asylum seekers living in Britain with their families, a Home Office minister has said.
More than 50 dog surfers of all breeds and sizes joined an annual dog surfing competition in California