David Cameron will fly to Sweden on Monday in a last-ditch attempt to prevent the appointment of Luxembourg’s former Prime Minister Jean-Claude Juncker as the next EU President.
He will meet the German Chancellor, Angela Merkel, and try to persuade her that Juncker is the wrong man for the job because British officials suspect he is one of a diminishing number of politicians who still believe in the concept of a United States of Europe.
Mr Cameron has promised that if he is returned to government next year, he will secure reforms within the EU and then put Britain’s continued membership to a referendum – but he fears he will get little co-operation from the EU if Juncker is at its head.
The Foreign Secretary indicated that failing to get the "right people" in the EU's top jobs would make it harder to renegotiate the UK's relationship with Brussels ahead of the in/out referendum promised by the Tories by the end of 2017.
Mr Hague acknowledged the UK could not veto Mr Juncker taking on the role, but the Government was attaching "great importance" to making sure that reformers took senior posts in Europe.
He told BBC1's Andrew Marr Show: "On the technical question of veto, this is now decided by majority voting in the European Union, taking into account the wishes of the European Parliament.
"But it's very important in our view that a range of candidates are looked at. This is only one of the top jobs being decided now in the European Union, there are four or five such jobs and it's very important there is a political balance, there's a geographic balance, it's important there are women in there in the top jobs in the European Union."
He added: "The important thing, and we haven't decided on the personalities of this yet, but the important thing is that the European Union is focused on reform, it's focused on change, it's not going to deliver what the people of any European country need if it carries on with just business as usual.
"The point that the Prime Minister has been making, that I have been making, is that the people who are chosen to lead the commission, the council, have to be chosen with that in mind."
Mr Cameron will travel to Sweden tomorrow for talks with the country's prime minister Fredrik Reinfeldt, Dutch counterpart Mark Rutte and Mrs Merkel on reforms in Europe, with the candidates for the commission and its presidency also expected to be on the agenda.