The money, released in the last three months from the Funders Contingency, is to make the venues more blast resilient, the Department for Culture, Media and Sport (DCMS) said.

The Funders Contingency, which is chaired by the Chancellor of the Exchequer Alistair Darling, and also consists of the Chief Secretary to the Treasury Liam Byrne, Olympics Minister Tessa Jowell, Secretary of State for Culture, Media and Sport Ben Bradshaw, Secretary of State for Communities and Local Government John Denham and Secretary of State for Transport Lord Andrew Adonis, is used to cover risks outside of the control of the Olympic Delivery Authority (ODA) which is in charge of Olympic build and infrastructure.

Decisions on resilience measures are being made with the latest advice of the security services before allocating funding.

In its quarterly economic report on the budget for the £9.325 billion Olympic project, the DCMS said: "£19 million of contingency has been released to enhance security resilience to the permanent venues.

"These are predominantly hardening modifications to existing structures.

"The forecast for security has not increased as this cost was included in the anticipated final cost in the previous report."

The current economic cris has forced organisers to dip into the contingency of which of £1.272 billion remains from the £1.972 billion available.

It was also confirmed that £3 million of the original budget for the basketball arena has been released back to the contingency as it has not been needed.

Jowell said: "On the eve of our three years to go celebrations the Olympic project remains on time and on budget.

"The overall funding package for the Games remains the same and the anticipated final cost of the ODA budget is the same as it was at the end of March 2009 - £7.234 billion."

Taxpayers have been forced to rescue the £1 billion Olympic Village after the collapse of a private-finance deal.

It amounts to a nationalisation of the 2012 construction project.

In May Ministers agreed the injection of £324 million takes public investment in the scheme to £650 million.

The £9.325 billion public sector funding package for the Games includes £6.1 billion for the ODA budget.

There is £2 billion contingency and £1.2 billion for non-ODA activities such as wider security and support for elite and community sport.

Jowell said more than 4,000 workers were now on the Olympic Park site involved in building venues and infrastructure such as roads and bridges.

She said: "The project continues to provide jobs and millions of pounds worth of business opportunities to companies around the UK in a challenging time."

ODA chairman John Armitt said it had hit all its targets in the past year.

He said: "Though we are making strong progress we are not complacent.

"The year ahead is a challenging one as activity on site reaches its peak."