The line underwent a five-month upgrade this year

Drivers had refused to work because of poor visibility caused by the dirt which has been created by engineering works, Transport for London said.

Maintenance firm Metronet said work had been undertaken over the weekend to grind the rails in the two tunnels.

The line reopened about 1125 GMT. It had been closed on Monday and again at 0750GMT on Tuesday.

Tunnel cleaning

A Metronet spokesman said services were suspended on Tuesday morning after a driver reported tunnel dust was obscuring his vision.

"Metronet was surprised there were problems with tunnel dust yesterday but this was resolved after a clean-up operation," he said.

He said there were no reported dust problems when the line re-opened on Monday afternoon or early on Tuesday morning.

"The only work carried out [Monday] night was to carry out further tunnel cleaning," he added.

'Terrible mess'

London Underground's boss Tim O'Toole said Metronet had failed to carry out enough dust suppression leaving a "terrible mess" on Monday.

He said: "Liquid was used to keep dust levels down but drivers complained they could not see the signals properly this morning."

The line reopened in September after a five month project to upgrade track and equipment.