A Leicestershire MP has apologised for taking a photograph during the State Opening of Parliament and posting it on the internet.
Parliamentary officials are investigating whether MP Liz Kendall breached regulations by taking the picture on her mobile phone on Tuesday.
The newly elected Leicester West Labour MP posted it on social networking website Twitter.
A spokesman said it appeared to be a breach of the rules.
A spokesman for the Sergeant at Arms office, which deals with regulation breaches, said it was "looking into the matter".
A House of Lords spokesman said: "It does appear there was a breach of rules."
Along with the photograph, Ms Kendall posted the message: ''Quick snap in Lords after Queen's speech, haven't quite managed to capture sheer number of diamonds and tiaras."
Ms Kendall said she has apologised to the Sergeant at Arms, adding that she was unaware taking pictures was not allowed.
She said: "Parliament is supposed to be for the people and I thought people would like to see what's going on in the state opening.
"Because it's filmed and broadcast live to the nation I didn't think there would be a problem.
"I didn't mean to break any rules of cause any offence, I just wanted to open up Parliament to the public."