The sculptor Antony Gormley has welcomed news that a campaign to raise £50m to buy a painting by Titian from the Duke of Sutherland has been successful. The purchase will be announced officially tomorrow.

Mr Gormley, one of 40 artists who signed a petition calling for the nation to buy two Titians being sold by the Duke, said the works – Diana and Actaeon and its partner Diana and Callisto – were "divine". He said: "They are an inspiration for everyone... a fixed point in the Scottish map of masterpieces."

The announcement is likely to reignite a political row in Scotland, however. Despite a public campaign, almost all the money has come from public funds, with a substantial donation from the Scottish Government – £17.5m, according to some sources. Ian Davidson, MP for Glasgow South West, said: "They are closing schools in Glasgow because they can't afford to repair them, yet we can find millions to give to one of Britain's richest men."

The purchase of Diana and Actaeon means that the National Galleries of Scotland and the National Gallery in London now have four years to raise a further £50m, to buy Diana and Callisto. The deal has been delayed by legal wrangling as galleries tried to get assurances that the Duke would not put any more works up for sale for 21 years.