Analysis By Nick Assinder Political correspondent, BBC News website

Gordon Brown is facing his first genuine domestic crisis less than a month after taking office.

Mr Brown has attempted to show he is in charge

The nationwide floods which have hit up to half a million people have proved the old saying that what politicians fear most is events.

And the way the prime minister reacts to the growing calls for action and concerns over existing emergency planning and future house building may well overshadow his carefully planned accession.

It has already proved bad timing for opposition leader David Cameron who, after visiting his flood-hit constituency, then flew out to Rwanda for a pre-arranged trip to underpin his strategy to tackle global poverty.

So, probably Mr Brown's first task was to demonstrate he had "taken control" of the crisis by visiting one of the worst hit areas and pledging to do everything necessary to tackle both the short and long term problems.

The visit was followed by the first of his "regular" press conferences back in Downing Street which he also used to insist he was doing everything necessary to tackle the immediate problems and plan for the future in a world struggling to come to terms with climate change.

But even as he visited Gloucester, he was facing claims that too little was done to prepare for the unprecedented downpours of the last two months - claims he and minister Hilary Benn denied during the Downing Street press conference.

New homes

And, it is hardly the best background for the release of his housing green paper - the central feature of his legislative programme.

A leaked draft of the paper says to ban building on flood plains would be "unrealistic".

Mr Brown wants to have 3 million new homes built, many of them in the south east of England, to tackle what is now generally accepted as a housing crisis.

Critics have attacked lack of preparation for floods

There have already been fears that might see incursions into the green belt - now there are more pressing fears that such a massive programme will see homes built in areas liable to flooding.

On the existing planning, Mr Brown echoed the view of the chairman of the Environment Agency, Sir John Harman, that the recent rainfall had been at an "extraordinary" level and insisted that current defences had protected many communities.

He also suggested there would be government cash to both help those in immediate need, and for longer-term flood protection measures.

Take control

Meanwhile, minister Yvette Cooper, in charge of the house building plans, suggested that opponents of the building programme were "playing politics" with the floods.

She said the rules were being tightened to ensure there was no building on land considered to be at "high risk" of flooding by the environment agency - a point also driven home by the prime minister.

But aside from all this detail, as others have found before him, it will be the way the prime minister "takes control" of the issue that will decide how he is perceived.

His decision to visit Gloucester showed he was aware of the need to be seen to be taking charge, rather than simply attempting to direct operations from Downing Street.

His aim was to reassure people that there would be money to help tackle the immediate problems - restoring power and water and offering shelter to those made homeless - as well as to pledge longer-term flood and coastal defence programmes.

He wants to reassure the public that he has a grip of the issue. But with more flooding expected, and opposition parties questioning the emergency preparations, this crisis seems far from over.