RAIL passengers whose festive travel plans were plagued by cancellations and disruption as a result of engineering works on the outskirts of London were let down by "significant weaknesses" in planning, a report has found.

Some 115,000 passengers using the East Coast Main Line between Christmas and New Year were left stranded after engineering works at King's Cross and Paddington overran, leading to the cancellation of hundreds of train services in and out of the stations on December 27 and 28.

An investigation by the Office of Rail Regulation (ORR) said Network Rail, the body in charge of carrying out the works, had "failed to put the impact on passengers at the centre of decision making".

Although Network Rail delivered more than 98 per cent of the complex engineering works planned for the festive period on time, the ORR's analysis found "significant weaknesses in the planning and oversight of the King's Cross and Paddington works".

It added: "The plans failed to put the impact on passengers at the centre of decision making, and this meant the service passengers received during the course of disruption was not acceptable and led to widespread confusion, frustration, discomfort and anxiety."

The investigation was conducted to learn lessons and prevent similar disruption in future. Network Rail is reviewing all contingency plans for works scheduled over Easter and the May 2015 bank holidays.

ORR expects Network Rail to have implemented all the recommendations, including those which require work with train operators, in advance of the Christmas 2015 engineering works.

The regulator will carry out an audit to make sure the improvements are all in place.

Joanna Whittington, ORR's director railway markets and economics and the investigation lead, said: "Network Rail has rightly acknowledged it didn't do enough for passengers affected by overrunning engineering works at King's Cross and Paddington this Christmas. While the company generally has a good record for delivering engineering work on time, in this instance passengers were really let down.

"Our investigation found that contingency planning did not fully consider the impact of potential overruns on passengers and that this needs to change. In future, plans will address the impact on passengers as well as engineering and train operation issues. Network Rail cannot achieve this alone, train operators will also need to play their part.

"Network Rail has committed to ensuring all work undertaken this Easter has a contingency plan which is fit for purpose, and to implement all recommendations in time for engineering works planned over Christmas 2015. ORR will audit its progress, to ensure that passengers' needs and safety are central to Network Rail's and train operator contingency arrangements."

Network Rail said it welcomed the report, which echoed the findings of its own investigation in January.

Mark Carne, chief executive at Network Rail, said: "Putting passengers at the heart of our planning is absolutely the right thing to do and we recognise that we let people down during the disruption experienced on December 27 and 28.

"Over Christmas, we undertook the biggest programme of engineering and investment work ever, upgrading train lines across the country. The overwhelming majority of this work went to plan but in the case of King's Cross and Paddington we accept we got things wrong.

"Our own report has caused us to look again at the work we have planned this year and the contingency plans we have in place and the ORR's report underlines the necessity of this work."