MPs will vote on the proposals, which will also allow civil partners to convert their partnership to a marriage and enable married people to change their legal gender without having to end their union, for the first time when the Bill has its second reading on Tuesday.
Backbenchers have made no secret of their opposition to the move and were left even more angered when the Tory leadership made clear it would not include marriage tax breaks in next month's Budget - something that would have been seen as a concession to disgruntled traditionalists.
The cartoon shows an angry-looking traditional Tory backbencher cutting a wedding cake with a chainsaw. On top of the cake, we can see a surprised David Cameron holding hands with an unidentified man. The symbolism should be self-evident once you're familiar with the context.