LONDON - The biggest shareholder in Sainsbury's, the Qatar Investment Authority (QIA), is selling 306 million pounds ($399 million) worth of shares in the British supermarket group, reducing its holding by about 5%.

Shares in Sainsbury's, which has an over 15% share of Britain's grocery market, trailing only Tesco, were down nearly 5% on Friday.

Regulatory filings show QIA offered 109.4 million shares at a price of 280 pence, with Goldman Sachs the sole bookrunner.

Prior to the offer, QIA had a 14.2% stake in Sainsbury's, according to LSEG data.

Sainsbury's stock closed Thursday at 288 pence, up 12% over the last year.

Monthly industry data has shown its food business performing well. However, its non-food business, which makes up a quarter of its sales, has been affected by UK shoppers' reluctance to spend on discretionary items.

A spokesperson for Sainsbury's declined to comment on QIA's move, while QIA did not immediately respond to a request for comment.

Qatar's sovereign wealth fund has been a Sainsbury's shareholder since 2007. That year its holding peaked at 25% and it abandoned a potential bid. It started selling in 2021.

"Given the strategic nature of the shareholder, we do not see it (the share disposal) being necessarily linked to upcoming events," said analysts at JPMorgan Cazenove, noting the government's budget statement on Oct. 30 and Sainsbury's interim results on Nov. 7.

QIA's other high profile UK investments include a stake in Barclays Bank and London department store Harrods.

($1 = 0.7664 pounds)

(Reporting by James Davey; editing by William James, Sarah Young and David Evans)