The pair, who previously owned Birmingham, took control of the Hammers in January when they bought it from Icelandic group CB Holdings.

They have now increased their share of the club from 25% to 30% each at a cost of £8million, with £4million going to CB Holdings and the other half to the club.

"We have a long-term intention of increasing our shareholding, while we have also invited professional investors to share in our vision for this special club," Sullivan said in a statement on the club's official website.

"Also, in the near future we hope to extend to supporters the opportunity to invest in the club.

"We are committed to putting West Ham on a firm financial footing that will form the basis, we hope, for success both on and off the pitch.

"Myself and David Gold are, like you, West Ham United fans and our aim is to ensure our club enjoys a stable and successful future.

"To this end, we have both invested a further £4million to increase our shareholding to 30% each."

Sullivan and Gold made public the scale of West Ham's financial problems following their takeover, putting a figure of £110million on the club's debts.

CB Holdings still own 40% of the club but Sullivan and Gold have a three-year option to buy those shares.

The pair sacked manager Gianfranco Zola on May 11 after the Italian had saved the club from relegation from the Barclays Premier League.

Their relationship with Zola was always difficult, with Sullivan describing the 3-1 defeat by Wolves in March as "pathetic".

Avram Grant is now expected to be named as the Italian's successor next week, following his resignation as Portsmouth boss.

Grant is currently on holiday with his family but is understood to have agreed in principle to join the Hammers.

Grant was top of a shortlist which was thought to have included Blackburn's Sam Allardyce, Blackpool's Ian Holloway and Cardiff's Dave Jones.

Grant worked wonders at relegated Portsmouth, taking the club to the final of the FA Cup, where they lost 1-0 to Chelsea.

The Israeli won many plaudits for the way he rallied the side when many of the players had their wages paid late and the club went into administration.

West Ham vice-chairman Karren Brady insisted today midfielder Scott Parker would be staying at the club.

The 29-year-old has been linked with a move to a number of other Premier League clubs, including Aston Villa, but Brady is adamant he is going nowhere.

"It's interesting that David Sullivan has given his word that Scott Parker will not be sold and I think that's absolutely what we wish to deliver to the supporters, that he's not going to be sold," Brady told BBC Radio 5 Live.

"So I think Aston Villa should reconsider making any approach because the worst thing is that it's very unsettling for the player, very unsettling for the club.

"I think if we wanted to sell him we'd go about it a different way but we really don't. He's the player of the year and he's very important to us in building a better team to take West Ham into a better future."