Tesco is preparing a charm offensive as it bids to build what would be the UK's biggest supermarket.

It wants to extend its Purley Extra store in south London from 82,000 sq ft to 139,000 sq ft, and is to begin a series of public consultations next month.

A key aspect of Tesco's plan to win local hearts and minds will be a pledge to get involved with London Mayor Ken Livingstone's push for more open spaces in the city. "We want to make the most of this site and we want to see if we can include an open community area in the development," said Tesco corporate affairs manager James Wiggam. But Tesco has been dealt blows elsewhere. It has lost a five-year battle to build a superstore on the former Vaux Brewery site in Sunderland, which it bought in 2002. Planning permission was not granted as the land was central to the Sunderland Arc regeneration plan. This week a public inquiry into the matter ruled in favour of Sunderland Council.

Another public inquiry has also ruled against Tesco. The retailer wanted to open an Express in Finchley, north London, but the inquiry upheld Barnet Council's decision to reject Tesco's application to take over a carpet shop.

The case hit the headlines earlier this year when Tesco was accused of using 'Trojan horse' tactics to get planning permission through the back door. Links were found between Tesco and Carpet 4 Less, which had gained permission to change the site from a petrol station and into retail space.

n Tesco's US operation has seen off a second attempt to get a temporary injunction on the construction of its distribution centre in Riverside, California.