THE decision to delay parts of a rail electrification project will “harm the health” of residents in Windsor and Slough, an MP has warned.

Fiona Mactaggart spoke out after the Government announced it is deferring parts of the £2.8bn project to electrify the Great Western route, including the line between Slough and Windsor.

The plan, already delayed, was to fully electrify the route from Cardiff to London by 2018, in order to eradicate diesel-powered trains and create faster, more reliable journeys.

A probe into the project, led by Sir Peter Hendy, chairman of Network Rail, led to a review of the works and government chiefs have now decided to defer parts of the project to free up between £146m and £165m.

The National Audit Office (NAO) said the estimated cost of the project since 2013 has shot up by £2.1bn to £5.6bn.

Rail Minister Paul Maynard MP said: “It is a project unprecedented in scale that is building on and around ageing assets in constant use.

“We have been clear that there have been difficulties with this programme. These were set out last year in the review of Network Rail’s delivery plan by Sir Peter Hendy.

“As a result of this scrutiny from the Hendy review I will defer four electrification projects that are part of the work along the Great Western route.”

Miss Mactaggart slammed the decision, which will see diesel powered trains continue to run in areas surrounding Slough and Windsor,claiming residents would continue to suffer poor air quality. .

She said: “The minister says that he can bring in the expected benefits without costly engineering works,” said the MP for Slough.“Trains every half hour between Slough and Windsor will continue to run on diesel and contribute significantly to the poor air quality which harms the health of people in Slough.”

The labour MP also accused Mr Maynard of ignoring health consequences, adding: “I have written to the minister asking what assessment he has made of the health consequences for local residents of this decision.

Adam Afriyie, MP for Windsor, agreed the decision was disappointing. He added: “It is important that passengers see the benefits of modernisation in the quickest, most efficient and cost-effective manner for taxpayers.”