The Leader of the Opposition said Labour MPs would only vote for a deal if it guaranteed “unfettered access” to the European market - something that has already been ruled out by the EU.
By raising the prospect of a Parliamentary rebellion against the deal Mrs May secures, the Labour leader has given EU member states a stick with which to beat the Prime Minister as she tries to get the best deal for Britain.
On Wednesday Mrs May will open the way for two years of negotiations with the EU when she invokes Article 50, the formal process of withdrawing from the EU.
In a letter to the European Council, Mrs May will set out in general terms her key demands for the deal.
Mr Corbyn told ITV’s Peston on Sunday: “We’re very clear that there has to be unfettered access to the European market, otherwise the threat to jobs in this country is absolutely huge.
“Most of our manufacturing industries have a European sale and European supply chain in them. And if we don’t maintain this unfettered access to the European market then quite clearly those industries are very much at risk.”
When it was pointed out to him that European leaders had ruled out access to the single market for post-Brexit Britain, he was asked if he was “basically committing Labour to voting against Brexit”.
Mr Corbyn replied: “No we’re not...we’re not at the position of knowing what the deal is yet.”
If Labour voted against the Brexit deal and persuaded enough Tory rebels to join them, it is possible that Mrs May could be defeated in Parliament when she presents the deal in two years’ time, meaning Britain would have to crash out of the EU with no deal at all.
Tory MP Philip Davies said: "He may be trying sabotage but it would be futile sabotage as we are either leaving with a deal or leaving without a deal. If he wants to leave without a deal then clearly he would be voting for the hardest possible Brexit. Is that what he is advocating?”
Mr Corbyn’s comments echoed the stance of the shadow Brexit minister Sir Keir Starmer, who told the BBC’s Andrew Marr Labour expected the Government to negotiate the “exact same benefits as the single market and the customs union”.
He said he was simply quoting an undertaking given by David Davis, the Brexit Secretary, to Parliament.
Iain Duncan Smith, the former Conservative leader, said Mr Corbyn’s demands were “absurd” and would simply be ignored by Mrs May and EU leaders.
He said: “What they are trying to do is sound like they have a view. They are being heavily criticised by their own party for having no line, and he is trying to give them something to hang onto.”