Rhona Hammond, agent for the North Colchester Conservative Association, backed a Sunday Express report that new members had been drafted into the Mistley branch from outside the area and some had given false addresses.
Sir Norman Fowler, party chairman, has ordered an inquiry into claims that the branch has fallen under the control of former National Front members and other right-wing extremists.
Sir Norman said he wanted to find out how the branch might have come to be controlled by people 'not remotely typical or representative of the Conservative Party'. He suspects 'dirty tricks'.
Mistley's call for the Prime Minister's resignation led to media claims that Essex Man had turned against Mr Major.
'To be a branch member you have to either live in the area or have a connection with it,' said Ms Hammond yesterday. 'Some gave false addresses and some claimed connection on the grounds that they helped the local MP's election campaign but we don't think they did.' Ms Hammond said the Colchester association had been concerned about Mistley since last April, when it split from neighbouring Manningtree. Since the split, the Mistley branch had demonstrated at events organised by Anne McIntosh, the local MEP.
When the association tried to oust members who had given false addresses, the members threatened legal action. 'We could not afford court action and so we backed off,' Ms Hammond said.
At last week's meeting, only 14 of Mistley's 51 members turned up for the annual meeting, where the call for the Prime Minister's resignation was passed 12 to 2. Ms Hammond attends all branch annual meetings.
'I tried to tell them it was a waste of their time,' she said. 'It is MPs who decide who the leader is. Since the meeting we have had letters from other members of the Mistley branch, who were not at the AGM, dissociating themselves from the vote.'
Comparing the case to Militant's infiltration of the Labour Party, she said Sir Norman wanted 'to nip it in the bud'.
A Conservative Central Office official said it was suspected that the branch had been taken over by people with views more akin to the British National Party than the Conservative Party.