Nelson Peltz, the activist investor who has been engaged in a bitter five-month battle with Heinz, is expected to win at least one seat on the board following yesterday's ballot on competing slates of directors.

However, the world's largest ketchup maker said final results of the shareholder ballot in Pittsburgh would not be known until mid-September.

William Johnson, Heinz's chief executive, said it could take three to four weeks to tally the results.

Heinz said several large shareholders representing more than 60 million shares voted yesterday - out of the more than 285 million share votes expected to be cast - but that it was "premature" to forecast the outcome.

The food company has hired an independent firm to count the proxy ballots.

Heinz said the company was happy with the results so far.

"It appears from preliminary results that Trian's attempt to secure a voting bloc of five seats and gain creeping control of the Heinz board has been defeated."

Mr Peltz could have enough votes for one or two seats, but it was too early to tell, the company added.

The Trian camp is optimistic it has gained at least one seat on the board, but cautioned that could change as large blocks of votes have yet to be counted.

If Mr Peltz or any of his four nominees are successful, it would restrict their ability to sell shares in Heinz, making it more difficult for them to dispose of their investment quickly.

Capital Research and Management, Heinz's largest shareholder with a 12 per cent stake, declined to disclose how it had voted.

Trian is the second-largest shareholder with 5.5 per cent of Heinz's outstanding shares.

Mr Peltz said the proxy contest had been an "arduous and hard-fought" battle. "Heinz brands are truly iconic but they need support, they need investment," he told shareholders.

"Our plan is very simple: invest behind the brand, get sales to go up and get expenses to go down."

Mr Peltz has been a vocal critic of Mr Johnson since he succeeded Sir Anthony O'Reilly in 1998. He has called on Heinz to cut $575 million (€448 million) in spending. Heinz, however, has urged shareholders to re-elect its directors and reject Trian's nominees. In June, the company announced measures to improve its financial performance, including cutting costs by $355 million over the next two years.

Thomas Usher, Heinz's presiding director, told shareholders the company was "not broken".