The proposals would bring sweeping powers over language law compliance
A bid by the assembly government for more powers over the Welsh language will be published this month.
But it is understood that the UK government's Welsh Secretary has reservations, warning it could face a difficult time in Parliament.
There is thought to be particular concern over the possibility of Whitehall departments being fined for not making sufficient use of Welsh
Delays in the proposals have led to tension between Labour and Plaid Cymru.
Correspondence seen by BBC Wales indicates fundamental issues around the use of Welsh have been the subject of intense discussions between the Welsh Secretary Paul Murphy, First Minister Rhodri Morgan and Attorney General Baroness Scotland.
The assembly government has been putting increasing pressure on the Wales Office to publish the document after a series of delays due to behind-the-scenes wrangles over its breadth and drafting.
Paul Murphy has warned some clauses could prove too controversial
The process, known as a legislative competence order (LCO) is the first stage in passing a Welsh law (measure) and will seek (in this instance) to give the assembly government more powers over the Welsh language.
It is expected to be published on or around 26 January.
If the LCO is approved the assembly government will introduce a measure (Welsh law) over the matter.
Before it is approved it has to be scrutinised by both the Welsh assembly and Westminster.
Royal approval for the LCO is then needed.
The Welsh Secretary has sent this LCO to his cabinet colleagues for their approval, the final stage of the process before it is published, with a 10-day deadline for them to sign it off.
It is understood the LCO, as currently drafted, would give the assembly government powers to enforce language equality, including for private businesses which provide services to the public, which could include water companies and even mobile phone firms.
Several Labour MPs have privately expressed scepticism about extending the scope of current language legislation to the private sector - a concern which has been intensified by the current economic climate.
Although Mr Murphy has agreed the assembly government can publish the LCO, so that AMs and MPs can begin their scrutiny, he has also issued a warning to ministers in Cardiff Bay that he fears some of the provisions will be so controversial that they may not survive into the final draft.
Both AMs and MPs can scrutinise the proposals once they are published
Until this week, Mr Murphy was refusing to include a clause that would mean Whitehall departments could face financial penalties for failing to comply with language equality legislation.
But officials in the assembly government were adamant it should remain, saying it would "focus the minds" of civil servants in England.
They point to the court service's introduction of the Libra system for issuing court summonses which was introduced with no provision to issue bilingual summonses.
Last month, the chair of the Welsh Language Board wrote to the director of the court services in Wales describing the situation as an "erosion of a long established Welsh-language provision and a blow to the status of the Welsh language within the criminal justice system in Wales".
Assembly government officials say the court summonses system is an "example of how easily language can slip off the radar".