Claims by a think-tank that the UK is a soft target for terrorists because of a loss of confidence in its identity have been rejected by the government.
The UK faces an implacable terrorist enemy, Rusi says
A Royal United Services Institute report criticised a "misplaced deference to 'multiculturalism'".
It says a cabinet committee should be set up to co-ordinate security.
But a Cabinet Office spokesman said some of the claims "do not stand up to scrutiny" and some recommendations had already been introduced.
The Rusi report was written by Professor Gwyn Prins of the London School of Economics and the Marquess of Salisbury, the former Conservative leader in the House of Lords.
Rusi says it is based on the findings of former military chiefs, diplomats, analysts and academics.
"The United Kingdom presents itself as a target, as a fragmenting, post-Christian society, increasingly divided about interpretations of its history, about its national aims, its values and in its political identity," it said.
"That fragmentation is worsened by the firm self-image of those elements within it who refuse to integrate.
"This is a problem worsened by the lack of leadership from the majority which in misplaced deference to 'multiculturalism' failed to lay down the line to immigrant communities, thus undercutting those within them trying to fight extremism.
"The country's lack of self-confidence is in stark contrast to the implacability of its Islamist terrorist enemy."
It added: "We look like a soft touch. We are indeed a soft touch, from within and without."
To deal with this and other threats such as global warming, and to restore public confidence in the country's overall security policy, the report suggests the creation of two new committees.
As well as the cabinet committee which would make a strategic assessment of the threats, it also suggests a joint committee of MPs and Lords to monitor security policy and identify any gaps.
However, a Cabinet Office spokesman said: "The safety and security of our citizens is the government's main priority, and the government rejects any suggestion that Britain is a soft touch for terrorists.
"Some of the recommendations made by Rusi have already been introduced by the prime minister.
"For instance a new National Security Committee is already established with a brief which includes international security, defence, counter-terrorism and community cohesion issues."
The spokesman said some of the report's other claims "do not stand up to scrutiny".
And he added: "The government firmly rejects the claim that the United Kingdom is a fragmented society."