The prospect of Britain's prison officers going on strike is likely to increase today when their union votes against a proposed pay award from the Prison Service. Industrial action by the Prison Officers' Association would be unprecedented and raises the prospect of the police or the army covering Britain's jails if the union's 35,000 members were to strike.

Tomorrow the union will publish the results of a ballot of its members which is expected to reveal their hostility to a 1.6 per cent salary increase proposed by the Prison Service Pay Review Body.

'The depth of feeling among the membership over this derisory pay award is very significant,' said Colin Moses, the union's chairman. 'At a time when the prison population is at crisis point, it is shameful that POA members are to be offered the lowest pay award in the public sector.'

If the union rejects the pay offer, as expected, it will then consider a range of options - including strike action. Under its contract with government the union is legally obliged to give 12 months' notice that this would be its members' intention. However, the union is exploring legal loopholes that might allow it to escape the contract.