Farron fears latest accord will rip the UK apart and lead to a united Ireland
Former Liberal Democrat leader Tim Farron has warned that Boris Johnson's last-minute Brexit deal with the EU risks breaking up the United Kingdom and leading to a united Ireland.
Mr Farron, the party's leader from 2015-17, also fears that the Prime Minister's proposed border in the Irish Sea will be permanent, posing "long term harm for the country".
The revised protocol announced yesterday allows the UK to leave the EU customs union as one. But the EU's rules and procedures on tariffs will apply in Northern Ireland for goods at risk of entering the single market.
It also effectively puts a border down the Irish Sea in terms of regulations.
Mr Farron said the backstop has effectively been replaced by Stormont, which will vote whether to continue to apply the arrangements four years after the end of the transition period.
He tweeted that "given that there will never be a unionist majority in the Stormont Assembly, Mr Johnson's proposed border in the Irish Sea will be permanent. It means the loss of Northern Ireland and then Scotland from the UK".
He later told the Belfast Telegraph that because Stormont "will never have a majority unionist block ... you will have different varieties of nationalists who will of course want to remain in a customs union with Ireland. Our sister party, Alliance, will choose the lesser of two Brexits - the softer version currently on offer under Mr Johnson for Northern Ireland as opposed to the harder one for mainland Britain.
"Those factors added together mean that the border in the Irish Sea would be absolutely permanent - that, in my opinion, is a racing certainty."
On the potential break-up of the Union, Mr Farron added: "The wonderful thing about being in the EU is that it allowed the border between the north and south of Ireland to be blurred without anyone having to lose. That was a fragile and marvellous thing and the Good Friday Agreement was a major part of all that.
"If you normalise Northern Ireland as being different from the rest of the UK, there is a pull factor which leads Northern Ireland to be on a trajectory for leaving the UK. If I was Scottish or Welsh, I would be looking at the Northern Ireland deal and thinking, 'Well why can't we be in a customs union with the EU?' - so it adds to the calls for the UK to be split up.
"While I want the UK to be in the EU, I actually want the UK to stay together even more than that.
"My hope is that people who may have favoured Brexit on balance, but who now see that the only price to pay would be the break-up of the UK might well see that is not a price worth paying.
"We will go from one damaging event of the UK's withdrawal from the EU - in terms of our influence, prosperity and place in the world - to then ripping ourselves apart.
"We're now beginning to realise that anything less than the single market or customs union membership means that you've either got the hard border or the border in the Irish Sea. They are both very damaging - the hard border in terms of peace and Northern Ireland's economy and the Irish Sea border in terms of the integrity of the Union."
Mr Farron said the idea that the House of Commons will vote through the deal at tomorrow's special sitting is "laughable" .
"Mr Johnson has set himself a target of Halloween, which no one asked him to set, so this is all about him being able to tick a box that Brexit is done. So for the short term electoral benefit of one man, it's long term serious disadvantage and disharmony for the whole UK," he added.