The shadow of Afghanistan loomed over a packed House of Commons today as MPs gathered for the first session of Prime Minister's Questions since the summer recess.

Gordon Brown, wearing a black tie, began by reading out the names of 37 British soldiers who had died serving in Afghanistan since the House last met. The moving tribute was heard in silence across the chamber. "Their lives live on in the ways they influence others," Brown said.

The Conservative MP Ann Winterton briefly lowered the tone in the House by asking a partisan question about the Lisbon Treaty. Would it, she asked, oblige the government towards further integration in the EU? The Prime Minister pointed out that Britain had joined the EU in the 1970s and remains obliged to its treaties while protecting British interests.

David Cameron, the Conservative leader, supported the Prime Minister's sentiments, declaring that the troops' "loved ones" would miss these men, not just today, but for the rest of their lives. He then ramped up the pressure on the Prime Minister by asking about an individual case to which he had been alerted, of a Territorial Army officer whose training was allegedly being cut. Cameron pressed Brown on resources for the war.

Brown said he would write to the Conservative leader about the case but assured the House that all was being done to provide the resources for this war.

Nick Clegg, the Liberal Democrat leader, joined the tributes and said the UK owes the 37 men an "imeasurable debt of gratitude". Clegg said that we also owe them tough questions: he asked about our mission and accused the Prime Minister of being "in denial" about the legitimacy of the Karzai administration, which he said should be urged to form a coalition government.

The Prime Minister expressed concern about the administration and the level of "ballot-rigging" that took place in the recent Afghan elections, but said it was "remarkable" that such elections had taken place at all amid an insurgency. He reiterated the claim that the British presence in Afghanistan protects our streets at home from terrorism.

The rest of the question-and-answer session passed largely without notable incident. The Tory leader may believe he just needs to "play it safe" and not put a foot wrong in order to continue to lead in the polls. He failed to land a glove on Brown today, but a full attack may not have been his intention. Bizarrely, there was no reference to the expenses scandal, though there was a question from the Tory MP Peter Bottomley about the injunction involving the law firm Carter-Ruck, which Brown said represented an "unfortunate area of the law".

It would be inappropriate to "score" this sombre PMQs, but normal service will resume next week.