Deutsche Boerse and the London Stock Exchange on Wednesday agreed to press ahead with their planned merger to create one of the world's biggest exchanges, insisting the tie-up will succeed irrespective of the outcome of the looming 'Brexit' vote on Britain's future in Europe.

The two operators said that they had agreed to proceed with their "merger of equals" under the key terms already drawn up.

The announcement comes as US-based global markets operator Intercontinental Exchange (ICE), which owns the New York Stock Exchange, is also mulling a rival bid for the LSE.

And it also comes at a politically sensitive time as Britain is due to hold a referendum on June 23 which will determine whether it remains in the EU.

LSE chief executive Xavier Rolet said  in a hastily-convened telephone conference that the tie-up with the Frankfurt exchange was "the right deal at the right time."

- No threat from Brexit -

And Deutsche Boerse CEO Carsten Kengeter said the plans would not be torpedoed even if Britain votes to leave the EU.

It will "succeed irrespective" of a possible Brexit, he said.

As already proposed at the end of February, Deutsche Boerse shareholders will end up with 54.4 percent of the new holding company's capital, and LSE shareholders with 45.6 percent.

Both financial markets would continue doing business under their respective current brand names.

The LSE and Deutsche Boerse are to become intermediate subsidiaries of the combined group, with the existing regulatory framework to remain unchanged.

The combined group is to be listed on both the London and Frankfurt stock exchanges and its shares included in the blue-chip stock indices EuroStoxx, DAX and FTSE.

It will have headquarters in London and Frankfurt and the board would have "equal representation" from both sides.

LSE chairman Donald Brydon will be chairman of the combined group and Deutsche Boerse chief executive Kengeter will assume the role of CEO and LSE's finance chief David Warren will be chief financial officer.

- 'World's biggest' -
The two sides described it as a "industry-defining combination" that would create "a leading Europe-based  global markets infrastructure group.

LSE chief Rolet said it would be the biggest stock exchange in the world in terms of combined revenue.

The merger would deliver "significant value creation through cost synergies of 450 million euros per year" and "significant opportunities for revenue synergies," they said.

The latest project is the third attempt to combine the London and Frankfurt stock exchanges.

In 2000, similar plans were blocked by the LSE's owners. And a second attempt in 2004 -- when then rival Euronext had made a competing bid -- the British hedge fund, The Children's Investment Fund (TCI), also derailed the plans.

On the Frankfurt stock exchange, Deutsche Boerse shares were showing a gain of 0.51 percent at 76.14 euros early Wednesday, while the overall blue-chip DAX 30 index was up 0.74 percent.