Indeed he did say both 5m and 4-5 ft, but Mr.Saffrons reply that the guy I replied to was referencing only mentions the 4-5 feet from the electricity distribution board.
Clearly he said 4-5 feet which isn't 5m or 15 ft 
Do you guys actually read and comprehend the set up described? The OP stated that the router will be positioned 4-5 feet from an electricity distribution board whereas the adsl filter would be 5m [15 feet] away. It seems that he comprehended that a phone extension lead would be undesirable and thought CAT5e would be better. Leaving the adsl filter in the phone socket and running a RJ11 extension lead, of appropriate quality, even of 15 feet in length, was all that is required and will work fine.
I have seen routers placed as close as 2 feet away from electricity distribution boards and have not noticed any degrading of network facilities, so no problem in the OPs siting of the router. 4 - 5 feet away. It is pure speculation that the [shielded] 5m RJ11 cable would run parallel to the mains cabling but even if it did is unlikely not to matter at all. Comments about running network cables parallel to mains cabling muddy the water with what the OP is trying, or will, do.