The Office of the Telecommunications Authority received 1,313 complaints of machine-generated nuisance calls in the first five months this year, the office's Assistant Director So Tat-foon says.

Speaking on a radio talk show this morning, Mr So said the office received 3,622 similar complaints last year.

He said the situation has improved since 21 telephone service providers joined a trial scheme to launch a voluntary code of practice for handling junk-call complaints in April.

Under the code, the service providers will initiate an investigation upon receiving two or more complaints against the same sender as identified by the telephone number.

The service providers may suspend or terminate the junk callers' telephone lines under the telephone service contract's terms and conditions if two complaints are found substantiated.

Noting the trial in April and May was successful, Mr So said the operators have terminated seven groups of telephone lines, reducing the number of junk calls by half.