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
PM Malcolm Turnbull said people convicted of terrorism-related charges would be held indefinitely if they pose an ongoing threat to society.
Democratic National Committee chair Debbie Wasserman Schultz stands down after leaked emails show party actively favoured Hillary Clinton.
The pair, believed to be the boy's mother and stepfather, were held after the five-year-old's lifeless body was discovered in a lagoon.