Barclays shares opened down 4.5% on Tuesday after one of the bank's largest shareholders Qatar Holding moved to sell around 510 million pound ($644 million) of its stock, cutting back on its crisis-era investment in the bank.

The sale was set to price at 141 pence per share, which was a discount of about 1.4% to Barclays' closing share price on Monday, one of the banks acting on the deal said overnight.

The share sale comes as Barclays embarks on a shake-up to cut costs and revive its share price, which has halved since Qatar first invested in 2008.

Barclays' share price was last down 3.4% at 138 pence and was set for its biggest one-day loss since Oct. 24.

($1 = 0.7925 pounds) (Reporting by Iain Withers and Danilo Masoni, editing by Sinead Cruise)