Will a phone ONLY extension cord affect broadband speed?

My router plugs into the socket just fine and being a router I can hide it away out of sight. The same can't be said for my landline and the nearest cupboard is a out 6 meters away! If I was to run a 10 meter extension cord that will be used with the phone only and left the router plugged directly into the master socket, am I likely to experience any sort of interference? I can find plenty of things about extension cables slowing down broadband but it looks like that's when plugging both the phone and broadband into the extension cable rather than just the phone.

Assuming the phone extension is plugged into the phone socket of whatever microfilter or DSL faceplate you are using then effect on the broadband should be zero

You mean have the extension lead for the phone plugged into the PSTN jack on the ADSL filter ? If yes, that�s all good.

I use DECT cordless phones for the landline. I tuck the base station out of sight, the phone only needs a charge every few days.