London Briefing:Perhaps Mike Ashley didn't quite catch what his PR flacks said when they urged him to embark on a "charm offensive" in the City.

After a tumultuous week that saw shares in his Sports Direct group plummet to less than half its February flotation price, bridges between the company and its investors badly needed to be rebuilt.

Only half the message seems to have got through to the maverick retail boss, however - and it certainly wasn't the bit about charm.

Investors nursing hefty losses on their Sports Direct investment must have choked on their cornflakes on Sunday morning as the reclusive billionaire broke cover in a rare newspaper interview.

Instead of donning sackcloth and ashes after last week's dire profits warning, Ashley embarked on an extraordinary diatribe against the City, branding investors "a bunch of cry babies".

"I've got balls of steel," he told the Sunday Times. "Some investors have been great and have been very supportive. But some of these City people act like a bunch of cry babies."

Emphasising his lack of remorse over the company's performance, the interview was accompanied by a new picture of the rarely photographed Ashley, posing outside his Lillywhites sports store in London's Piccadilly with his fists raised, combat-style.

He might just as well have raised two fingers to the City. His provocative stance has further enraged investors who paid 300p for Sports Direct shares in February only to see them trading now at less than 150p.

Ashley, who retains control of the company with 57 per cent of the shares, has also seen the value of his investment crumble, although he has the consolation of having cashed in shares worth £929 million (€1.38 billion) in the float.

He spent part of that on the £133 million takeover of Newcastle United football club, a move which sounded alarm bells among investors who saw it as a further distraction from Ashley's day job.

In its brief time as a public company, Sports Direct has generated more negative headlines than some companies do in a decade, from its two profit warnings to the abrupt departure of its chairman and its refusal to answer the City's questions or publish current sales figures.

Then there's the astonishing way in which Ashley settled an argument with his advisers over a £200,000 legal bill - by a game of Spoof.

Ashley lost that one but other risks have paid off - he used a £180 million chunk of his flotation profits to buy up shares in the German sportswear manufacturer Adidas.

He sold the 3 per cent stake just weeks later, banking a profit of £29 million.

That was a personal punt by Ashley but, in another bizarre development last week - and just two days after its profit warning - Sports Direct revealed that it, too, had bought a stake in Adidas.

Analysts were baffled by the motivation behind the £48 million share purchase, saying, "You couldn't make it up." Others complained that the company should concentrate instead on improving its sickly sales rather than punting stocks.

If there was ever any doubt that Ashley couldn't care less about City conventions, it was dispelled in his combative comments over the weekend.

As well as the cry babies jibe, Ashley insisted investors in Sports Direct "got exactly what it said on the tin" when they bought their shares, adding that the company "should come with a government health warning - this stock is not for the faint-hearted".

He is clearly enjoying his role as the enfant terrible of the retail world, taking an almost childish pleasure in winding up the City suits - or in leading them astray, as he did when he persuaded one of the City's most senior investment bankers to play that game of Spoof.

The City can be remarkably tolerant of the unconventional - if Sports Direct was doing well, then Ashley could get away with almost anything. What it does not like is losing money. The Sports Direct funder may also come to realise that the City has a way of getting its own back on those who do not play the game.

Ashley will need his investors' support if he is to fulfil his ambition of turning the group into the world's biggest sportswear business; after all, that was the sole reason he chose to go public after so many years avoiding the spotlight.

The time for baiting the City will be when Sports Direct shares have recovered to a comfortable premium to their flotation price. Until then, another lengthy period of silence might be in order for Ashley.

Fiona Walsh writes forthe Guardian newspaper in London