The US parent company of Kettle Foods said its net income had grown by 58pc following the takeover of the crisp firm, which has a manufac-turing base in Norwich.

Announcing its results, Diamond Foods, which bought Kettle in a �403m deal in March 2010, said that retail sales of Kettle crisps had grown by 10pc, with growth driven by a strong performance in the multi-pack Kettle Ridge crisp line.

In the US sales of Kettle Crisps had grown by 11pc, giving it around 10pc of the market.

The results showed gross profits of $251m (�159m) in 2011 up from $161m (�102m) in the previous 12 months while Diamond incurred $16.8m (�10.6m) in 'acquisition and integration' costs related to the purchase of Kettle Foods and the pending acquisition of Pringles.

Kettle has seen significant growth since being bought by the San Francisco-based firm, with sales up 13pc in the 12 weeks to December 25, with its Norfolk workforce increasing by about 50 to 409 last year.

In February the owners revealed a �6.2m expansion in its Norwich factory in Bowthorpe, while in April it announced a deal to buy the Pringles Snack brand.

Michael J Mendes, Diamond chairman, president and CEO, said: 'Our base Diamond business delivered record financial results this quarter, with our snack portfolio up a solid 16pc on an organic basis.

'We're particularly pleased that we could achieve such strong performance while effectively managing the Pringles integration.'

It said that it hoped to complete the merger in December after being given the final clearance to press ahead.