The Prime Minister, who postponed the weekly Cabinet so that he could visit waterlogged Devon, announced he was cancelling a visit to the Middle East next week to focus on the plight of Middle England.
In his first Downing Street press conference for almost 240 days, Mr Cameron made clear no effort would be spared to help the flood victims but he could give them little hope that the relentlessly stormy weather would break any time soon.
"There is absolutely no sign of this threat abating," he declared. "Things might get worse before they get better."
The Prime Minister underlined how the experience of being flooded was terrible, telling reporters: "I've seen it in my constituency, I've seen it over the last couple of days. It's ghastly when your house is flooded with water, you've got to take all the plaster out, the furniture is wrecked, it takes a long time to recover. It is a really painful and depressing process."
His warning of a "long haul" came as the Environment Agency (EA) said rises in the level of the River Thames were set to further disrupt flood-hit areas.
Around 1000 properties have been reported as flooded in the past week alone, including 800 along the Thames.
Kate Marks, an EA senior flood adviser, acknowledged it was "increasingly likely" there would also be problems along the River Severn and River Wye on the England/Wales border.
Yesterday, 16 severe flood warnings, 133 flood warnings and 225 flood alerts were still in force.
"Money is no object in this relief effort. Whatever money is needed for, it will be spent," Mr Cameron insisted, rejecting calls for the £11 billion foreign aid budget to be raided to help the flood-hit communities. He said that the UK was a wealthy enough nation to do both.
He accepted the military could play a bigger role and said by the end of yesterday some 1600 service personnel had been deployed, with thousands more available.
The Prime Minister announced that a new Cabinet committee to oversee the recovery would be established and that he would chair its first meeting tomorrow.
Mr Cameron also revealed that a tax deferral scheme would help businesses hit by flooding while up to £10 million in new funding was being found to support farmers; grants for homeowners and businesses would be available to improve flood defences.
He made a point of praising the work of the EA staff but again offered only limited support for its under-fire chairman, Labour peer Lord Smith. The PM said there would be a time to "discuss how the pendulum against dredging swung too far in the past and how we put that right in the future" but brushed aside talk of dismissals, insisting that right now "everybody needs every minister, every head of an agency, everyone involved, to work together to deliver the best possible response we can to these floods and that is exactly what is happening".
He vowed lessons would be learned, adding: "We will deal with the floods and we will build a more resilient country for the future."
Elsewhere, Ed Miliband was accused of visiting a flood-hit village for a "photo opportunity" by local Tory MP Alok Sharma.
The Labour leader was told by the backbencher to ask residents if "they welcome you here or not" as he toured Purley-On-Thames, Berkshire, to see the damage it had sustained over recent weeks.
Mr Miliband insisted his visit was "not about politics" but about co-operation.
He told Mr Sharma: "What I suggest is that you and I go and talk together to the residents in a sign that this isn't about politics, this is about working together."
l Royal Bank of Scotland is offering three-month mortgage repayment holidays to customers with flooded homes. The group, which includes NatWest, is to unveil details of the scheme today.