The France prop Christian Califano, among a clutch of signings to be unveiled by Saracens on Thursday, is being sued by his former club Toulouse for nearly £1m for an alleged breach of contract.

The 29-year-old Califano has spent the year playing for Auckland Blues in Super-12, and Toulouse expected him to return to their ranks in September, having effectively been given a sabbatical by the club he joined 10 years ago.

So when Califano signed for Saracens a month ago, Toulouse tried to have the move declared illegal on the grounds he had signed a pre-contract committing him to the club until 2005. Under French law, however, Toulouse's only redress is through the civil court system, and now the club's president René Bouscatel is to submit a claim for €1.5m (£960,000).

The amount has been determined by the years Califano spent at Toulouse, plus the three years of service the club claims it will miss out on.

"Christian had a legal as well as a moral obligation to come back to Toulouse and we were very surprised when he signed for Saracens," said Bouscatel. "He signed a contract with us until June 2005; we only let him go to New Zealand because it was an ambition of his, and his contract clearly stated he would play for us on his return."

But Califano retorted: "It was my right to sign for Saracens and I have no intention of going back on the move. I was a free agent after coming back from New Zealand."

Califano is backed by the organisation which runs professional rugby in France, Ligue Nationale de Rugby, which does not recognise pre-contracts for players.

This is not the first dispute Saracens have had with the French game. The club is still to be paid compensation by the French Rugby Federation after the injury suffered by their outside half, Thomas Castaignède, while on international duty in November 2000. Castaignède damaged his Achilles tendon and only returned to action six weeks ago. Saracens paid his wages for the 18 months he was out of action, but contend the FFR should reimburse them.

Saracens will introduce Califano at Vicarage Road on Thursday along with the Leicester fly-half Andy Goode. The Tigers' centre Leon Lloyd is also a target for Buck Shelford's side.

Meanwhile Sale have confirmed they are unlikely to play at Heywood Road next season, after being told by the council to remove a temporary stand.

"We need better facilities and there is nothing available in the Trafford area," said the Sale chairman Brian Kennedy, who has been linked with an attempt to buy Bury FC and play rugby at Gigg Lane.