International Trade Secretary Liam Fox said the recruitment meant the UK was ready to take full advantage of the opportunities of breaking free from the European Union.
The team will also assist the campaign he is spearheading to build trade relationships around the world, promoting British exports and foreign investment into the UK in the run-up to Brexit Day.
His department was created by Theresa May when she became Prime Minister last year, to help Britain make the most of life outside the EU.
Opponents have derided the Government for being short of trade negotiators to hammer out deals.
Since Britain joined the EU it has relied on Brussels negotiators to make trade agreements on the bloc’s behalf.
But Dr Fox has told the Daily Express he now has more than 100 people on his team with direct experience of trade talks in a range of different EU and other international institutions.
In total, the department’s specialist Trade Policy Group which includes policy-makers, analysts and lawyers has grown from zero in July last year to more than 450 today.
More than 200 speak more than one language but not all have direct trade talk experience.
Overall Dr Fox’s department employs more than 3,740 people including a global network of more than 1,380 dedicated to promoting British goods and services abroad and attracting inward investment.
Dr Fox said: “We have reached a milestone and this means we are ready to take advantage of the opportunities to grow our trade relationships across the world and negotiate trade agreements that benefit the whole of the UK.
“Not only does my team have experience of working within key multilateral organisations, including the World Trade Organisation, the EU and the United Nations, we have also people with experience from across the private sector.
“We are geared up to negotiate deals that deliver benefits to all sizes and sectors of business, from all areas of the UK, which will result in jobs, growth and savings for consumers throughout Great Britain.”
Recently Dr Fox was in Argentina for the biggest-ever gathering of the WTO – its last major gathering before the UK leaves the EU in 2019 and becomes eligible to resume its own seat on the 164-country body.
He told an audience in Buenos Aires: “People across the world are waking up to the opportunities that Brexit will bring in terms of the UK forging new relationships.
“The International Monetary Fund projects that around 90 per cent of world growth is likely to come from outside the EU, so as an international economic department we need to be where the developing markets are.”
Earlier this year Dr Fox told our sister paper the Sunday Express he was proud of the “A-Team” of “young and dynamic” staff he was building from inside and beyond the Civil Service to help make a success of Brexit.
Last week Theresa May said Britain would aim to strike and if possible sign trade deals with non-European countries during the transition period that she wants after formal Brexit Day to smooth the changeover.
EU officials say signing deals would breach the rules of the transition but Britain thinks it is only the implementation of them that would have to wait.