In the UK, no. However the covert and defence service have the right to tap any wire, if they have suspicions that somebody may endanger the security of the government or military. I.E Terrorism.
In the U.S Although its rumoured that they have technology that can listen to all calls, and voice recognition software that will listen out for certain key words. If said keyword/s is spoken, they will then monitor all future calls from that line more closely, and suspect, a breach in security. All of this is conspiracy theory and can't be proven or disproven.
The U.S. laws are different and the services can at will retrieve data on the calling and called number, time of call and duration, which is collected automatically on all calls and stored for later use by the billing department of the phone company.
Bottom line, for the UK, your safe from big brother. It contravenes public privacy laws.
In the U.S be careful what you say on the phone if your harbouring terrorists.
If your concerned, these links will make your hair stand on end :
http://www.voanews.com/english/archive/2006-01 /2006-01-01-voa34.cfm
http://www.computerweekly.com/Articles/2008/05 /22/230779/revealed-government-plans-to-tap-ph one-and-internet.htm