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**Exhibit 31.1**

**CERTIFICATION**

I,John J. McDonnell, Jr., certify that:

1.             Ihave reviewed this quarterly report on Form 10-Q of TNS, Inc.;

2.             Basedon my knowledge, this report does not contain any untrue statement of amaterial fact or omit to state a material fact necessary to make the statementsmade, in light of the circumstances under which such statements were made, notmisleading with respect to the period covered by this report;

3              Basedon my knowledge, the financial statements, and other financial informationincluded in this report, fairly present in all material respects the financialcondition, results of operations and cash flows of the registrant as of, andfor, the periods presented in this report;

4.             Theregistrant’s other certifying officer(s) and I are responsible forestablishing and maintaining disclosure controls and procedures (as defined inExchange Act Rules 13a-15e and 15d-15e) and internal control over financial reporting (asdefined in Exchange Act Rules 13a-15f and 15d-15f) forthe registrant and have:

a.             Designed such disclosure controls and procedures, orcaused such disclosure controls and procedures to be designed under oursupervision, to ensure that material information relating to the registrant,including its consolidated subsidiaries, is made known to us by others withinthose entities, particularly during the period in which this report is beingprepared;

b.             Designedsuch internal control over financial reporting, or caused such internal controlover financial reporting to be designed under our supervision, to providereasonable assurance regarding the reliability of financing reporting and thepreparation of financial statements for external purposes in accordance withgenerally accepted accounting principles.

c.           Evaluated the effectiveness of theregistrant’s disclosure controls and procedures and presented in this reportour conclusions about the effectiveness of the disclosure controls andprocedures, as of the end of the period covered by this report based on suchevaluation; and

d.           Disclosed in this report any changein the registrant’s internal control over financial reporting that occurredduring the registrant’s most recent fiscal quarter (the registrant’s fourthfiscal quarter in the case of an annual report) that has materially affected,or is reasonable likely to materially affect, the registrant’s internal controlover financial reporting; and

5.             Theregistrant’s other certifying officer(s) and I have disclosed, based onour most recent evaluation of internal control over financial reporting, to theregistrant’s auditors and the audit committee of registrant’s board ofdirectors (or persons performing the equivalent functions):

a.             All significant deficiencies and material weaknesses inthe design or operation of internal controls over financial reporting which arereasonable likely to adversely affect the registrant’s ability to record,process, summarize and report financial information; and

b.             Any fraud, whether or not material, that involvesmanagement or other employees who have a significant role in the registrant’sinternal control over financial reporting.

DATE: July 21, 2006
|  /s/ JOHN J. MCDONNELL, JR.      |   |   |
|---------------------------------------|--------|--------|
| John J.  McDonnell, Jr.          |   |   |
| Chairman and  Chief Executive Officer |   |   |

 

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