A flood of “asylum seekers” has blown the federal government’s immigration detention budget, the opposition says.

Opposition immigration and citizenship spokesman Scott Morrison said the government had been forced to more than double the money it allocated in the last budget for offshore immigration processing. “In the May budget the Rudd government had allocated $125 million for offshore processing,” he said in a statement today. “However additional estimates figures reveal the government is now asking for another $132 million for this work, an increase of more than 100 per cent.”

The claim comes on top of the arrival of another boatload of asylum seekers in Australia’s northern waters today and fears the detention centre at Christmas Island will be unable to cope with further arrivals.

The boat was intercepted by HMAS Armidale at 11am (AEDT) about 11 nautical miles (20km) north of the Ashmore Islands, the federal government said. Initial indications suggest 89 passengers and four crew were on board. The group will be transferred to Christmas Island where they will undergo security, identity and health checks and their reasons for travel will be established.

It is the 10th asylum seeker boat to be intercepted in Australian waters this year. The Rudd government is under pressure over its border protection regime with detention facilities on Christmas Island at breaking point. There are already almost 1,800 detainees in immigration facilities on the island which have a capacity of 1900.

Mr Morrison said the government’s border protection policy had failed. “Barely a day after 89 asylum seekers were flown to the Australian mainland in a futile effort to reduce overcrowding on Christmas Island, another 89 asylum seekers plus three crew are on the way to take their place,” Mr Morrison said. “Seventy-eight boats have now arrived since the Rudd government started weakening the border protection regime they inherited from the coalition government, with 10 arriving this year alone with 602 people on board.”