The company behind the proposed redevelopment of the Natwest Tower in the centre of Birmingham said more than a third of its assets either increased or held their value in the period since March.

In a sign of increased confidence, British Land said its properties were worth £8.2 billion at the end of June, a fall of 3.7 per cent on three months earlier and better than the 9.2 per cent fall reported in the previous three month period.

The best performance came from superstores – accounting for 13 per cent of its estate – after the portfolio increased in value by 0.6 per cent and rental values rose 0.4 per cent. This was offset by a drop of 6 per cent for its shopping centre estate, although this was better than the 10.8 per cent decline reported earlier in the summer.

The company’s other interests include a 50 per cent stake in the Meadowhall shopping centre near Sheffield and the Broadgate office development in the City of London. Tesco and Sainsbury’s both account for 6 per cent of the company’s total rent, while major office customers include Royal Bank of Scotland.

British Land reported a 9 per cent drop in its net asset value to 361p a share. The decline in this key measure was smaller than expected and caused shares to open in positive territory yesterday.

Chief executive Chris Grigg said the pace of decline in the company’s portfolio valuation “slowed markedly”, with £3?billion of assets either remaining steady or appreciating in the quarter – equivalent to 39 per cent of its estate.

Meanwhile, reports have linked a group of high-profile investors to a possible bid for British Land.

The office and shopping centre owner is said to have attracted the interest of Indian steel magnate Lakshmi Mittal and the Abu Dhabi ruling family.

Reports said bankers from Credit Suisse had been asked to prepare a possible bid that could be worth as much as £10 billion.