With Labour winning seven Scottish constituencies at last year’s general election, another 20 seats would see Mr Corbyn’s party taking almost half of the 59 Commons seats north of the Border.
In his address at Dundee’s Caird Hall, the party’s UK leader will declare that “Labour in Scotland is back” and claim Labour is preparing for government at Westminster.
But Mr Corbyn was yesterday ridiculed by opponents after an advance copy of his speech appeared to suggest that he was unaware how many Scottish seats his party actually won last year.
“We won six seats for Scottish Labour at the last general election and we are on the cusp of winning around 20 more,” a trail of Mr Corbyn’s speech said.
In fact, Scottish Labour won seven seats. The party gained an extra six seats on top of Edinburgh South.
Scottish Conservative deputy leader Jackson Carlaw said: “Even with just a handful of Scottish Labour MPs Jeremy Corbyn can’t get the number right. This blunder shows exactly how much attention he pays to events north of the Border and the Scottish Labour branch office. He can’t have been much of a secret agent when he gets muddled up on simple arithmetic like this.”
Mr Corbyn is due to say: “This time last year there were more than a few people in the media who had written the Labour Party off. In Scotland we were told that Labour was dying.
“The truth is that we very much are alive and kicking. Labour in Scotland is back. Of course I know that we didn’t quite win [last year’s general election]. But we are no longer just an opposition. We are a party preparing to go into government.”
On Brexit, Mr Corbyn will say that the Conservatives’ Brexit plans are “in chaos”.
“At one of the most important times for our country in its history, we have a divided government that has no clear idea of what it’s doing, what it wants, or where it’s going.
“And as Theresa May has now admitted, under her plans for a reckless Tory Brexit, the UK risks losing access to European markets.
“Make no mistake about it, reduced access to European markets means fewer economic opportunities for people in the UK.”
He will also accuse the SNP of wooing Donald Trump to build his golf course in the North East of Scotland.“While the SNP wooed Trump to build his golf course in Aberdeen, and Theresa May appeases him as she bets the UK economy on a race-to-the-bottom trade deal with the US, Richard has shown Labour is standing up to oppose the racism, misogyny and dangerous belligerence coming from the US administration.