Foreign Office Minister Bill Rammell has held key Tory target Harlow in Essex after three recounts.
Bill Rammell just pipped the Conservative candidate
Mr Rammell's victory over Conservative Robert Halfon by 97 votes takes Labour's total seats to 356, with the Tories on 197 and Lib Dems on 62.
Officials had called off the second recount at 0600 BST on Friday, claiming staff were too tired to continue.
They resumed their efforts at 1000 BST. Labour won the seat in 2001 with a 5,228 majority over the Tories.
Mr Rammell told BBC News he was relieved he had won and that Labour had succeeded nationally.
He said Labour needed to "do more to listen and respond and persuade people".
He said: "The team we've got at the top, particularly Tony and Gordon, are very very effective and although this is not as good a result as the one we had hoped for, it is the first time we've ever been elected three times in a row.
"I remember the 1980s, I remember when Labour supporters wondered whether we would ever win again."
Harlow Council said the decision to delay had been taken by the returning officer after consultation with legal advisers.
Around 80 volunteers had begun work at Harlow Sports Centre at 2130 BST on Thursday night, with the first ballot box arriving at 2220 BST.
The last constituency to declare will be Staffordshire South, where the vote was called off following the death of the Lib Dem candidate last week.
That seat, being defended by Conservative Sir Patrick Cormack, is set to be run as a by-election in a month's time.