SPORTS Direct is being investigated by advertising watchdogs over an allegation of misleading pricing of its Rangers shirts online.

The Advertising Standards Authority is probing a complaint that the Mike Ashley-owned company was misleading fans by stating that blue home shirts listed online had been reduced from £59.99 to £47.99 when actually they had been at the lower price since release day.

The ASA examined the complaint and confirmed that it will be investigated, saying Sports Direct will be contacted for their comments.

The complaint challenged whether "the savings claim was misleading and could be substantiated".

Two weeks ago Sports Direct hit back at the makers of a Channel 4 Dispatches documentary which shed light on the business practices of the company, including details of its discount pricing strategy.

The sporting goods retailer was accused of claiming £74.99 trainers had been 'discounted' to £59.99 when in fact they had never been on sale at the higher price.

A group spokesman said at the time: "It seems clear that Dispatches has selected only a tiny minority of discounted products from the thousands that pass through Sports Direct's retail channels at any one time."

One complainer has been told by ASA that after an "initial assessment" of the complaint it was decided that further investigation was needed.

They are seeking evidence for the general selling price of the Puma Rangers home shirt.

Sports Direct last year saw sales jump 24 per cent to £2.7 billion and pre-tax profits increase to £207 million.

Mr Ashley, the 22nd richest person in Britain with a fortune of £3.5bn, also owns Newcastle United and has a 8.9 per cent stake in Scottish Championship club Rangers.

Fans have protested over deals done by a previous Rangers board and Mr Ashley that has resulted in his Sports Direct empire having control of the club's retail operation, including its stores.

The Herald revealed in February that the Sports Direct founder and owner is the "ultimate controlling party" of Rangers Retail which handles the club's merchandising, including the selling of Rangers shirts.

Mr Ashley's control over retail and trademarks comes as a by-product of his £5m emergency loan to Rangers made in January.

Rangers Retail was set up as a joint venture between the club and Sports Direct and was promoted as enabling Rangers "to once again control its retail operation and give supporters the chance to buy direct from the club and in doing so, continue to invest in its future".

In December, fans group The Rangers Supporters Trust launched a bid to take on Mr Ashley, by launching an alternative shirt for fans saying all profits will be ploughed into an increased shareholding in the club.

The new blue strip, priced at the time at just under £33, followed a red and black version previously released.

An ASA spokesman said: "I can confirm that we are formally investigating whether the savings claim for a Rangers home shirt on the Sportsdirect.com website is misleading. We will publish our findings in due course."

Sports Direct did not respond to a request for comment.