Three of Oxford's park-and-ride sites could be left without night-time security if workers decide to strike.

Nine of the 12 security guards responsible for patrolling the city council-run Pear Tree, Seacourt and Redbridge park and rides will this week ballot for industrial action.

The row comes after staff refused to work alone at the sites after dark. They say the decision is about cost-cutting, which could put their lives at risk.

However, the council has said it has carried out a proper consultation and the new scheme will be enforced.

One worker, who did not want to be identified, said: "We have to deal with drug dealers, drug users, car thieves, joyriders and travellers. It is just not worth the risk. We're not prepared to do it."

Staff say there should be 15 security workers across the three sites which would allow them to "double up" at night, but recently employees have left and not been replaced. The nine workers involved are members of trade unions Unison and the Transport and General Workers' Union (TGWU).

The sites are currently manned from 7am until 11pm with workers paired up after 7pm.