Former West Ham winger Trevor Sinclair has turned up the heat on the club's owners David Sullivan, David Gold and Karren Brady.
West Ham manager David Moyes kept the Hammers in the Premier League last season but they suffered a 2-0 home defeat by Newcastle in their opening game on Saturday and they have not made a new singing this summer.
Pressure has been mounting on unpopular owners Sullivan and Gold and vice-chairman Brady with some fans supporting the GSB (Gold, Sullivan, Brady) Out campaign.
And now Sinclair, who made close to 200 appearances for the Hammers in five years at the club, has intensified the pressure on the hierarchy at the London Stadium.
He has criticised the board for not backing Moyes in the transfer market, writing on Twitter: 'If you can't or won't back Moyes and invest in players needed then sell. #GSBOUT.'
That Tweet on Sunday night followed his thoughts following the defeat by the Magpies on Saturday evening, where he said: 'Great transfer window for Newcastle and this was a must win for West Ham looking at our fixtures, long season ahead unless signings made.
'If #GSB haven't got the funds to invest in players why not sell the club to a buyer that has the funds and wants to resurrect our club.'
Sinclair then uploaded a picture of himself playing for the Hammers alongside the message: 'Some care more than others.'
West Ham are the only top-flight club not to bring in a new recruit this summer and the scrutiny on the club's board has increased in recent weeks following the sale of Grady Diangana to West Brom.
Captain Mark Noble was left seething with the club after the winger was sold to a Premier League rival for £20million, explaining that he was 'gutted, angry and sad' in a Tweet.
Other players showed their support for Noble, as Chelsea target Declan Rice liked his skipper's Tweet and Jack Wilshere commented on Diangana's Instagram post.
On a post where the 22-year-old thanked West Ham for his time with the club, the former Arsenal man did not hold back as he commented: 'Go and do your thing in a club that respects you. big player with a big future.'
