There is a long paper The Case against the Covenant
There are 10 reasons to vote against, with a brief explanation of the background
and there is a 3-point summary.
All papers are in Word or pdf format.
These are the three points:
We’d lose freedom
The CofE would surrender its right to decide for itself how best to serve the people of England: it would have to limit itself to what was acceptable in all countries and cultures.
It’s hugely over-centralised
Under the guise of recommendation, the 15-person Standing Committee would have great new powers: if the Standing Committee went against decisions of our PCCs & Synods, the CofE could be excluded from the Communion’s main bodies.
New developments would be shackled
Changes such as remarriage in church after divorce, and women’s ordination, might never have happened with this Covenant in place: our Church would lose its ability to develop and to respond to new situations or fresh insights, and could find itself forced to exclude ideas and people it wanted to include.