William Hague has offered to help Nigeria secure the release of more than 200 schoolgirls kidnapped by Islamist militant group Boko Haram.
The pledge by the Foreign Minister came Tuesday, after the children's kidnapper reportedly said he would sell them.
The US has already condemned the kidnapping of hundreds of school girls aged 16 to 18 as an "outrage" and has vowed to help release them.
"We are offering practical help," Hague told reporters as he arrived for a Council of Europe meeting in Vienna to discuss ways to defuse the situation in Ukraine, where the government is trying to quell an insurrection by pro-Russian activists.
"What has happened here... the actions of Boko Haram to use girls as the spoils of war, the spoils of terrorism, is disgusting. It is immoral," he said.
He said he did not want to discuss the details of what help Britain was offering and stressed that the principle responsibility for dealing with the incident rests with the government in Abuja.
Boko Haram will "sell your girls in the market", the terrorist leader vowed Monday in a chilling video message to parents of the kidnapped schoolgirls.
"I abducted your girls. I will sell them in the market, by Allah," Shekau said, according to AFP. "We are holding people [as] slaves."
The girls should be married, not in school, he continued, according to the BBC.
"God instructed me to sell them, they are his properties and I will carry out his instructions.
Authorities searching for the missing girls say dozens have escaped from their captors but 276 are still missing. They were taken three weeks ago from their school in Chibo.
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Protests for the missing Nigeria schoolgirls
Protests have been staged in Nigerian cities over the failure of the administration of president Goodluck Jonathan to take action to return the schoolgirls to their families. Nigerian police say that some 276 girls remain in captivity, while 53 have escaped.
Speaking ahead of a meeting of the Council of Europe in Vienna, Mr Hague said: "It is disgusting, it is immoral, it should show everybody across the world that they should not give any support to such a vile organisation.
"Our hearts go out to (the girls') families. I called the Nigerian foreign minister when this first arose back on Good Friday, in the middle of last month, to offer help from Britain, to express our concern."
Asked how Britain might be able to assist the Nigerian authorities, Mr Hague said: "I don't think it's possible to go into the details of precisely what help we could provide, but we have offered assistance, our High Commissioner in Nigeria continues to offer assistance. We continue to discuss that with the Nigerians.
"Britain is offering assistance, but of course the primary responsibility for dealing with this rests with the Nigerians and we hope they will do what is necessary to reunite these girls with their families."
Mr Hague will host a summit in London next month of the Preventing Sexual Violence Initiative, which he launched in 2012 in response to the issue of mistreatment of women and girls in conflict areas.
"This is to help countries, including Nigeria, improve the way they tackle the consequences of sexual violence and make sure that those responsible can be brought to justice, that the evidence is gathered, that those who are victims of it can be properly looked after in the future," he said.
"Recently we've persuaded Nigeria to support that campaign, so this in the future may help. Of course, it doesn't help today with the situation of these girls."