Prime Minister Gordon Brown has rejected criticism from five former military chiefs about the treatment of and funding for the armed forces.
He said he had "nothing but praise" for the forces and was putting more money into defence "than ever before".
Former chief of staff Lord Boyce said making Des Browne defence and Scottish secretary had been an "insult".
Tory leader David Cameron has written to Mr Brown asking him to divide the roles between two people.
Asked about the criticism, the prime minister, who is in Kampala, Uganda, for a Commonwealth summit, said: "I have got nothing but praise for our armed forces.
"I have visited them in Iraq and Afghanistan and what they are doing are acts of great courage.
"I want to see the armed forces properly equipped with the resources that they need. And that's why we've been increasing expenditure on defence compared with the cuts under the previous government."
Earlier Des Browne told BBC Radio 4's Today programme that being Scottish secretary did not detract from his role as defence secretary, as most of the Scottish post's powers were now devolved to Holyrood.
"I will put my record in relation to both commitment and delivery up against anyone's," said Mr Browne.
"This is not an issue that has ever been raised with me by any serving soldier."
Total MoD spending for 2007-08 is set at £33.4bn, but the cash or near-cash figure is £30bn; this has been used above to allow historical comparisons and does not include capital charge
He said morale was high among troops in Basra, the UK's defence budget was second only to that of the US and it would see an increase of £7.7bn over the next three years.
On Thursday five former chiefs of the defence staff had warned, during a debate in the House of Lords, of "blood on the floor" at the Ministry of Defence because of inadequate funding.
The government's commitment was "best exemplified by the fact that the prime minister can't be bothered to appoint a minister in charge of the armed forces on a full-time basis", said Admiral Lord Boyce, who retired as chief of defence staff in 2003.
He questioned the government's claim that it was overseeing the longest period of defence spending since the 1980s, saying the cost of military equipment was rising faster than budget increases.
'Rethink dual role'
And Britain was "vastly exceeding" planning assumptions made in 1998, because of commitments in Iraq and Afghanistan, he said.
On Friday, former head of the Army, Gen Sir Mike Jackson, added his voice to the debate by saying the budget discrepancies were not a sudden event.
"This didn't happen overnight, this imbalance, and the prime minister now was, of course, the chancellor during the 10 years over which this tempo has accelerated."
Shadow defence secretary Liam Fox said: "The government needs to accept that there are shortcomings at the present time which it still seems to be in denial about."
In his letter to Mr Brown, David Cameron wrote: "At a time when our forces are engaged in two highly dangerous missions in Iraq and Afghanistan, the need for the defence secretary to be able to concentrate full-time on his role is surely a matter of plain common sense."
The Liberal Democrats' acting leader Vincent Cable said criticism had been "personalised" against Gordon Brown because, as chancellor "he signed the cheque for £5bn for the war in Iraq at a time when the armed forces were already overstretched.
"That is why the troops are under-equipped, they are not properly housed, they are not cared for when they are injured - and they are very angry."
Organisations like the Royal British Legion say the armed forces are over-stretched and under-funded, and say that while 4.4% of GDP was spent on defence in the early 1980s, today the figure is about 2.3%.
BBC defence correspondent Caroline Wyatt said the real question was whether the armed forces were being asked to do too much on the available resources.
Long-term defence planning failed to predict that Britain would be fighting two medium-sized campaigns on two fronts simultaneously, and facing lengthy ongoing commitments as a result, she said.
The last full review, which tried to match the armed forces to the threats they expected to counter, was carried out in 1998.
"The overstretch in the budget has led to calls from some for a new strategic defence review, which would outline exactly what military role and aims Britain wants to pursue - and how much it's prepared to pay for that," our correspondent said.