A leading Liberal Democrat MP who missed a crucial vote on anti-terror proposals has blamed Parliament's security measures for making him late.
Dr Cable has written to complain about security
The government only averted a Commons defeat on its Terror Bill on Wednesday by one vote - the closest margin since Labour came to power in 1997.
But Lib Dem Treasury spokesman Vincent Cable was late as he had to meet constituents outside.
Security procedures had delayed them for several hours, he said.
Another Lib Dem MP, Alan Beith, also missed the vote - he was giving an address at the funeral of a close friend in his constituency.
Dr Cable told the BBC News Website that queues for the Commons had been busy because of large numbers of trade justice campaigners.
The MP for Twickenham, west London, said: "Many people stood around in long queues. People had to get through interminable delays.
"In the middle of the afternoon I got quite angry. People from my constituency couldn't get anywhere near.
"I went out too see them and talk to them. By the time I had found them I could have just said hello and goodbye but that would have been impolite."
When Dr Cable returned, the divisions had closed. Had he been able to vote, the votes would have been level and the speaker would have had to give his casting vote in favour of the government's original proposal.
He said: "It didn't seem quite so dramatic at the time. We were required to be there and I was there. I was very cross that I had to miss the vote."
Dr Cable has written a "polite but critical" letter to the Serjeant-at-Arms, calling for swifter security procedures.
He said: "Quite apart from the problem of the vote, it's bad for the image of Parliament that people take the trouble to come up and are not allowed to see their MP."
Lib Dem chief whip Andrew Stunell said it was not reasonable for Mr Beith to be in Parliament and with hindsight Mr Cable had been doing one job too many by trying to meet his constituents.
But he told BBC Radio 4's World At One it would have been a "nice technical knock out" to have defeated the government.
But he argued it had persuaded ministers to climbdown on plans to increase detention powers in terror cases.
"What it did do is show the government that it had no chance with the most important and the most controversial part of the legislation."
Mr Stunell said nine Conservatives had also missed the vote.
In March this year, 17 Lib Dem MPs missed a key vote on different terrorism plans.
But the chief whip denied his party was at all "lacklustre" in such issues, saying the Lib Dems alone voted unanimously against the Iraq war and university top up fees.