The investment banker suing Mike Ashley has been accused of "making up evidence" by the head of the Sports Direct founder's legal team.

Barrister David Cavender QC told the High Court in London that Jeffrey Blue, who has sued the tycoon alleging Ashley did not hold up his end of the bargain on an agreement between the pair, launched the case an "opportunistic try-on".

"The claim appears to have been issued on the basis that the threat of negative press alone would compel Mr Ashley to settle," he told Mr Justice Leggatt on Tuesday (4 July).

"In truth, there was no purported agreement and Mr Blue could not have thought so at the time."

The issue stems from a conversation between Ashley and Blue, which allegedly took place in the Horse & Groom, a London pub, in 2013. The latter maintains the former promised to pay him £15m ($19.5m) if Blue agreed to use his expertise to double Sports Direct stock price to £8 per share within three years.

In his written opening remarks, Cavender added Ashley recalled having a conversation with Blue but he remains adamant no deal was agreed.

"He [Ashley] does recall 'that there was a lot of banter and bravado'," said Cavender.

"He does not recall any discussion about whether Blue would be paid a sum of money if the share price reached £8 a share. He says if there was 'it would have been obvious that he was joking'."

When the trial began on Monday, Blue stated he had received £1m from Ashley, instead of the £15m he was allegedly promised.

"I can't believe that [Blue] is now trying to take me for £14m off the back of some drink banter that he is seeking to engineer into something more," the Sports Direct founder told the court.

During yesterday's hearing, the court was told Ashley's business practices contravened "business orthodoxy".

The controversial tycoon, whose fortune is worth in excess of £2 billion ($2.7bn), allegedly lay under tables to take a nap during work meetings he found boring and played "spoof", a drinking game, to decide who would pay for an investment bank's fees.

Ashley, aged 52, who remains Sports Direct's largest shareholder, refutes the claims, branding them "extremely vague".

The Newcastle United owner is also alleged to have vomited into a fireplace after a Sports Direct management meeting, during which he reportedly drank 12 pints and vodka chasers.

The claim states Sports Direct's directors held a senior management meeting once a week at The Lion Hotel in Worksop, a short drive away from the firm's headquarters in Shirebrook, Derbyshire.

"These meetings were like no other senior management meeting I had ever attended in all my years of investment banking experience," Blue told the court.

"On one such evening, in front of his senior management team, Ashley challenged a young Polish analyst in my team, Pawel Pawlowski, to a drinking competition.

"Ashley and Pawel would drink pints of lager, with vodka chasers between each pint, and the first to leave the bar area for whatever reason was declared the loser.'

"After approximately 12 pints and chasers Pawel apologised profusely and had to excuse himself. Ashley then vomited into the fireplace located in the centre of the bar, to huge applause from his senior management team."