In any negotiation process all participants need to be conscious of an inherent risk, namely, that their own participation creates a sense of ownership and attachment.

The long hours, the focus on one new draft after another can cloud the original objective. The desire to produce the right deal can be superseded by the perceived need to produce a deal.

This is why all negotiations need measures to prevent this, a check mechanism and preferably multiple ones.

With the current UK-EU negotiations, there are two identifiable check mechanisms or lines of defence to concluding an unwise agreement - Cabinet and Parliament.

Last week, I wrote to the Prime Minister outlining broad concerns about the direction of travel.

This could be discerned from shifts in public comments, private engagements and what was being briefed in London, Dublin and Brussels. I wrote in the hope of reassurance and with the desire that an acceptable deal for us all was within grasp. Instead, I received confirmation that we were right to be concerned.

If what is outlined in the reply is the type of deal the Prime Minister intends to conclude, then the DUP could not support a deal which annexes Northern Ireland from the rest of the United Kingdom.

Indeed, many others in Westminster and throughout the United Kingdom, true to their commitments to respect the referendum, the national interest and to the Union, have contacted me to voice their concern.

Equally we cannot be assured that this current proposal will be the final deal. The European Union 'price' for agreement appears to rise daily whether it be our fishing industry or an ever growing list of level playing field commitments.

Last December when this 'backstop' appeared we were deeply concerned. This is why we sought and got the paragraph 50 assurance of a democratic protection against a sea border.

In March, the EU made clear its intention to ignore paragraph 50 and rewrite paragraph 49. We took no solace from our predictions being correct but we did take solace that it was universally rejected.

Neither the passage of time nor the application of pressure has made it any more acceptable now.

The 'new' idea of a UK customs arrangement does not appear to be a genuinely UK-wide offer but a GB offer and an NI offer badged as one - Northern Ireland in THE EU customs territory and GB in A customs union.

The real intent is not to solve any land border issues in Ireland but to handcuff the UK to the EU, with the EU holding the keys. The United Kingdom would be trapped.

The focus on customs arrangements should never blind anyone to a sea border of regulations.

We certainly did not forget it and why we raised it repeatedly and consistently.

It was something the Prime Minister ruled out after Salzburg: "…no new regulatory barriers should be created between Northern Ireland and the rest of the UK unless the Northern Ireland Executive and Assembly agree."

The limited and low level checks that exist at the moment in Belfast and Larne do not compare to what wo uld be the future arrangement.

Key industries in Northern Ireland would be subject to rules and standards with no democratic input to them. Rules would be made in Brussels rather than Stormont or Westminster.

The regulatory sea border with some caveats in the Prime Minister's letter is still a sea border.

This is not haggling about checks but preventing Northern Ireland from being left in the EU with the Northern Ireland Assembly reduced to vassal status or the devolution settlement torn up.

Our most important trade flows are to be hampered and regulated by the EU. Despite all of this a Northern Ireland specific backstop still remains.

The Scottish Conservative MP Ross Thomson has rightly warned: "…Northern Ireland would diverge unconsciously from the United Kingdom against the expressed will of its people - it would also feed Scottish nationalist demands that a similar divergent arrangement be made for Scotland."

The DUP does not stand alone against this proposal. We appreciate the support from MPs across the United Kingdom.

We are ready to stand with those in Cabinet and in Parliament to work for a better deal. One which works for the whole United Kingdom. We want the referendum result to be respected and the entire United Kingdom to leave together with a sensible deal.

Arlene Foster is leader of the DUP

Belfast Telegraph