A Cabinet minister said she was "absolutely gutted" to have missed the crucial Commons vote on Syria last week.
International Development Secretary Justine Greening was in a room just yards from the Commons chamber but claimed not to have heard the bell which summons MPs to the lobbies to cast their votes.
Greening and Foreign Office minister Mark Simmonds missed the key vote on David Cameron's motion on Syria, which resulted in a shock Government defeat by a majority of just 13.
The Prime Minister said he had accepted an apology from the pair after they failed to back the Government's motion setting out the case for potential military action.
Greening voted against Labour's rival motion but failed to take part in the second division which followed immediately after the result of the first one had been announced in the Commons.
The two ministers are understood to have been involved in a discussion on Rwanda in a room close to the Commons chamber.
Greening told BBC Radio 4's World at One: "We were in Parliament and indeed I has having a meeting with Mark Simmonds, Foreign Office minister, at the time, between votes, I voted in the first vote.
"Unfortunately for us we were in a room that it proved, apparently, that you cannot hear the division bell from."
She added: "We were unaware the vote had been called because we were unable to hear the division bell. This is the key bell that MPs have relied on literally for 150 years to tell them what's going on in Parliament.
"It was deeply unfortunate and I was absolutely gutted to have missed the vote. I promptly apologised to the Prime Minister but ultimately whether or not Mark Simmonds and I had passed through the lobby would not have made a difference to the result.
"We now need to listen to that result, accept it, which is what we have done, and we have been very clear as a Government that it means we will not participate in any military action."
After the incident last week House of Commons officials insisted there was no problem with the bell system and said it "would have been clear that there had been a division on".