Conservatives Robert Halfon, MP for Harlow, and Thurrock's Jackie Doyle-Price have written to government ministers outlining their concerns.
Chief Superintendant Sean O'Callaghan, of Essex Police, said action had been taken where appropriate.
Harlow and Thurrock councils said they had been doing all they could to deal with illegal sites.
Harlow has seen 68 unauthorised sites set up in the last year - a problem "echoed in Thurrock", the MPs said in their letter to the Home, Communities and Justice secretaries.
They claimed Essex Chief Constable Stephen Kavanagh had failed to uphold the law and deal with the issue effectively.
The MPs also criticised the force's crime commissioner (PCC) Nick Alston for "his failure to represent the views of residents in Essex".
Mr Halfon told BBC Essex his constituents had been complaining about anti-social behaviour and the rubbish left behind by travellers.
"The police commissioner, instead of being a poodle for the police's bureaucracy, should be a bulldog for residents of Harlow and Essex," Mr Halfon told BBC Essex.
He called for a zero-tolerance policy on anti-social behaviour, adding that authorities should use "all laws available" to move illegal travellers on.
PCC Nick Alston said he had been involved in several public meetings about the issue, and held regular discussions with the chief constable.
He added it was crucial the situation was dealt with "proportionately and fairly".
Ch Supt O'Callaghan told BBC Essex the sites were assessed on an individual basis and visited regularly by officers.
Harlow Council said it was doing all it could "within the constraints of current legislation".
A Thurrock Council spokesman said action had been taken to remove travellers who were in breach of planning law.
Illegal traveller sites are not being dealt with effectively by police and councils, according to two MPs.