A major increase in the UK commitment to help French and African forces in Mali and the region has been confirmed by Downing Street and the defence secretary, Philip Hammond, in an urgent statement to the House of Commons.

Amid concerns on the Tory benches that Britain is being drawn into a conflict without an exit strategy, the government said that 200 UK troops would train an African regional force outside Mali, with up to 40 more on an EU training mission inside the country. A further 70 RAF personnel will oversee the use of Sentinel surveillance, to be based in Senegal with 70 supporting crew and technical staff, and 20 will staff a C-17 transport plane for a further three months.

Britain has offered a roll-on, roll-off ferry to help transport French armour to Mali by sea, landing on the African coast. Britain is also offering air-to-air refuelling capacity to operate outside the UK, but based in Britain. It is possible the US will provide air-to-air refuelling.

Hammond outlined the British assistance after an urgent question to the Commons was granted by the speaker, John Bercow, in response to a request by the Tory MP John Baron.

The defence secretary said: "I can assure the house that we will not allow UK personnel to deploy on any mission until we are satisfied that adequate force protection arrangements are in place."

Britain is to offer £3m to help the African-led International Support Mission to Mali (AFISMA) to uphold a UN security council resolution on Mali. A further £2m will be donated to a second UN fund to build political stability inside Mali.

Hammond said: "The UK is also prepared to offer up to 200 personnel to provide training to troops from anglophone west African countries contributing to AFISMA, though the numbers required will be dependent on the requirements of the AFISMA contributing nations."

Baron raised concerns about the growing mission. "It is quite clear that British involvement is deepening in Mali and the wider region. I don't think there is any dispute that it is in everyone's interests that we do not allow legitimate government to fail, particularly when faced with extremists."

Baron, who said he opposed the military action in Afghanistan, Iraq and Libya, added: "I do fear one can be drawn into ever-deepening conflicts. Afghanistan illustrated in particular the danger of being sucked into larger deployments. The mission changed from defeating al-Qaida to nation building and the mission morphed into something much larger."

British sources stressed again that the UK would have no combat role in Mali, but disclosed for the first time that Britain had offered to run with the French a combined joint logistics headquarters inside Mali. The UK made the offer at a meeting in Paris on Monday attended by the prime minister's national security adviser, Sir Kim Darroch. The offer was rejected by the French at this stage as unnecessary, but shows the scale of the UK's preparedness to help its closest military ally in Europe.

The offer of 200 troops to train members of the AFISMA regional force is being made by the UK deputy national security adviser at a meeting in Addis Ababa on Tuesday.

The prime minister's spokesman stressed the UK military assistance was to "work out the appropriate support to regional forces". No timetable was given for the length of the UK commitment. "We will do what we can to help the French mission and to contribute to a regionalised approach," he added.